If you want to build quality modules there are a few things to keep in mind, though every player's taste is different, as some like RP, some like story, and some like action, so obviously you should pick what niche you are building for. Moreover, unless you are doing something purely for RP value, it should be kept in mind that this is a "Fantasy" game, not a game of "Realism", nor should we put a precedence on the latter.
Some of the best balanced modules I've seen don't go around nerfing (Restricting or changing things to make them virtually ineffective or unusable) everything, but they don't go about creating a Montey Python world either, where items & magic are handed out like candy at a candy store. The best modules I've been on use +6 AC items and +8 weapons, this tends to give a good balance, and monsters can still hit the players (though not all builds mind you), though, rather than trying to make monsters pound on the best builds, you should focus on balancing between the weaker & stronger builds, and every monster needs a weakness the players can exploit. (That's really what makes the game so enjoyable and fun to me & many other players)
Power is not something many builders are likely to hand out, some focus on letting a classes' abilities or skill shine, rather than making gear a precedence, some make gear a precedence, and others make magic / spells a lot more powerful (The base spell system is sorta weak to be honest). Some give precedence to classes, being partial maybe (I dunno), like making clerics really powerful, or fighting classes (Like Ranger, as we seen on Paths of Ascension), and though I'm not telling you how to build your module, I'm just pointing out that while you can do whatever you want, you should keep in mind that balance is crucial to pleasing more players.
If you start creating +7 or +8 or higher AC items (Unless it's limited to like just armor), then you are likely to throw balance of the core game completely off, not that you would find such items on most RP / Social / Story modules mind you, and not every class needs to have high AC. Barbarians and Dwarven Defenders get damage reduction, so that helps them take more hits, they also get higher hit points.
Dwarven Defender is a very powerful class on low level item modules, shifters can be too, if the player is highly skilled, but let's not focus on powerful class combinations, that's the fun of playing the game for the player. I've found that, no matter how awesome you make your monsters, a high level party will likely be able to withstand anything you throw at them. (Unless it's like completely overbearing, like 10 bosses, etc)
Therefore, when building, you need to focus on building for both single players soloing your module and parties as well, for even just 2 or 3 people in a party and the game changes significantly, in favor of the party mind you. A cleric & bard in a party can really make a party very powerful, likewise a single mage can as well.
On low level item modules magic tends to take a front seat, though you'll see builders go about nerfing spells, it's not something I'd recommend if you are building a fighter like module, for mages have lower hit points, and you need to balance magic vs melee very carefully! Handing monsters +6 or higher weapons pretty much renders most damage reduction spells worthless, except epic warding of course, and there truly is a lot to keep in mind while building monsters & your module, for caster monsters are generally despised by players a lot, especially the ones that spam magic missles / dispels / timestop, or other very annoying spells.
More importantly, remember the player is the hero of the story, not the peasant who needs to be controlled, and this is a game of fantasy, not one where players need to experience the drudgery & every nuisance you can concoct to throw at them or make them endure. We aren't trying to control the players, because players love freedom, and the perfect example of what not to build is a catacomb dungeon with very limited options, meaning they player is playing in a maze where monsters are around every corner, it just gets old fast.
We don't want to overwhelm players with excessive monsters (tedious and annoying to many players), neither do we want to underwhelm them (Starving players for XP / spawns) by putting 2 monsters on every map, and we don't seek to tax their spirit by making them crawl 16 x 16 maps without haste until level 20 to ensure they don't get anywhere anytime soon. (Don't be a jerk, please)
Make the game enjoyable, fun, and rather than focus on control, put a precedence on impressing players with good area & monster design. I assure you that any long time player knows the difference between a well done module and a poorly constructed one, mainly because they've had to endure some really messed up server modules, and I'm not really bashing any builders here, but some of were completely asinine while building.
If you want to be remembered for being a great builder, then build to please, and not to tease, have a great hook / storyline. Some of the best modules I played on were not confusing, didn't treat players like they were unwanted, and kept them living in the drudges of despair till the builder felt like giving them something nice. No, that's just not what you should focus on, and proof lays in the experience of the adventure, so do yourself a huge favor and run the adventure just like your players will be forced to, don't give yourself powerful items and say "It's too easy"!
Take the time to playtest your module through and through, are you advancing too slowly? (Borish) Are you advancing too quickly (Will require your module to be greatly focused on higher level play, e.g. a lot of level 40+ Adventures), or are you starving for gold? Module economics are also important, because It creates pack rat players if you starve players for gold, you'll see them running around collecting treasure / drops, and packing it back to the local merchant to offload them for gold continually. (A very borish task.)
Of course some players enjoy the whole clicking a gazillion times to acquire a million gold, but I for one DO NOT, and if you want to be a great builder, keep in mind that some players may be suffering from tendenitous or repetitive strain injury (clickalot), and we don't really want to click on stuff continually! Don't be stingy, but don't be too lavish, meaning having players with like 200 million gold in their account in a week, because that's a balance issue right there.
Some builders compensate for their poor building skills, by limiting items sold in stores to make gold practically worthless, but what fun is that? If you want to be a great builder, then learn to create fun & enjoyable modules, not lame stuff nobody wants to endure, and many of us players have endured some really messed up stuff in the history of this game. (Losing all your gear on death was probably the worst, I just logg off)
These aren't pot shots at bad builders, these are pointers to help you NOT become one of those builders who puts a precedence on the wrong things, it's a fantasy adventure game, not a rat trap dungeon where we need to control players in every possible way we can concieve! Don't put precendence on minor things like poisons, traps, and such, these are minor things that are easily overcome usually (unless the builder feels like making every step or dagger a monster has deadly, which is silly.).
What fun is it if your players die frequently? I for one despise seeing my characters die, it means I failed to play them well (to me), and if the module is too overbearing, then I concede that I cannot play the module and leave. If you want to make it hard for players, at least wait till they are a high enough level and have acquired some friends to help them out, sheeze! (Stop screwing with the noobs or you won't have any!)
Keep a careful eye on your DMs if you are running a server, listen to the feedback & complaints from your players, for some of the DMs out there don't have the foggiest idea what this game is about (Fun). Do yourself a favor and don't think for a moment if you build this grand module that's ultra pretty, that you'll have a lot of players, Neverwinter Nights exceeds the scope of most novice builder's ideas of what this game is by miles, and believe me I've seen a lot of stuff in my many years of playing this game.
The best builders are long time players who have had to endure a lot of BS, they wouldn't make other players endure it, and they know what ticks them off, so learn what ticks your players off! I've tried to keep the complianing to a minimum, but if you hear your players complaining, you better listen up and change something, or the complaining will lead you to bad reviews &/or an empty server! Make it fun for all, unless your focus is specifically an adult only server, but playtest playtest & playtest some more!
The best modules are those that have a great pleasant experience long after the player has advanced to higher levels, so don't go thinking you're going to build a great module in a few weeks, no it can take you a very long time, and you can get burned out trying too hard too fast. Be paitent, do adventures and areas with care, but don't spend too much time on things, test & finalize EVERYTHING! (That's a very important thing to remember!)
I've lost many projects to failure to test them thoroughly, after I had thought I was finished, when I went back later I found bugs / issues galore! When you are building a big module, it would be wise to build in test module seperately, after they are thoroughly tested, then you can import them safely into your main module. This is why I build systems one by one now, cause I know the headaches of importing stuff into large modules!
As your module grows, be sure to get veteran player's feedback, but also listen to the newbs, because they too may have a few bones to pick about it, and don't be afraid to change what players don't like! I tell you, a builder who builds to please will far excel those who ignore those they are seeking to entertain! Being a builder is much like being an entertainer, those who entertain the best, will get the most praise, and those who build like players don't mean nothing, will hear complianing galore!
Also, remember time, because a lot of players can't spend many hours playing, so don't make adventures longer than an hour in game play, strive for less if you can, and though this shouldn't apply to all adventures, this of course can be ignored if you are using location saving, so players can recall back to where they left off. The more options and stuff you give your players, the better experience they have, the less stuff you give them, the less fun they have, and that applies to so many things (Like adventures & NPC interaction), not just items.
If you want to rise to the top, then take the time to learn how to build well, scripting isn't that hard, and a large portion of adventures on big servers with nothing but monsters is BORING, so learn to put in tricks / traps, and some RP along the way too. What fun is it if everything is monotonous & linear? Keep it simple, keep it fun, but try to put something different in everything adventure you create, because variety is the spice of life! (Not realism & monotonous drudgery!)
Cheers, I hope someone enjoyed this short dissertation...