Magic item availability
I have been playing D&D since I got the red box in Jr high school. Over the years I have noticed a fundamental shift in how magic (items) is generally accumulated. In the beginning, you really only got them when you defeated something that either used it against you, or was guarding it cause it could not use it except as a lure for fresh prey. With third edition (and beyond, but I am a staunch non supporter of the latest version), you could see the fundamental shift in how things were approached by the creation of rules allowing for the design and creation of any magical items. You no longer needed to go out of your way to find that perfect item by rumour, research, or hardcore adventuring, you could just design your character, or if you were in a monty haul group, buy what you needed for that next adventure. As a DM, I have used the same campaign arc (well, I do travel alot, so I get fresh players) for the last 15 years. With each new group, things do change, even outside of the upgrade from second to third edition. The one thing that never changed, and I guess this is my main contribution to this thread, I still made certain that the party would be able to come across any special magic they needed during the course of the adventure. I made sure they knew it before they created their characters and reminded them periodically as they went along.
As an example, suppose they came to a point that they needed to do some underwater searching (adventuring). Prior to this point in the campaign, I would have made sure that each member of the party had a way to circumvent the whole breathing underwater bit before they came to the situation, or provided within the framework of that portion a way to get what they needed. If they squandered the resource because of poor planning (i.e. selling 'useless' magic), then they would have to pay through the nose, after considerable searching and travel, to replace it from some disreputable magic shop (the cost of security in those places is staggering, so of course things are expensive, it is bcause of the overhead of course). After which, I would remind them that they accumulate magic for a purpose and that purpose is not to sell it just because it does not appear to be readily useful. One time, I had a party that tried to sell an item none of them could use because of an alignment restriction. Everything was going fine, until they discovered, via ambush, that the purchasers could not afford it, so they tried to steal it (hey, they were evil after all). To make matters worse, someone else decided they wanted the item also, so it became a double ambush. I swear I did not plan any of it, I made it up as I went along. I really did not expect the party to try and sell the item and they were not getting the hint when no shops would buy it....After the double ambush, they decided that to destroy the item was the better course anyway (even though it was not necessary to the plot, they were good characters and they really did not need alignment problems because they were just getting greedy. The magic they wanted was just so expensive and they were not getting upgrades from me fast enough).
Anywho, I rambled long enough. In short, give out whatever is necessary for plot advancement through 'random' or 'placed' treasure, and just make up the rest of it as you go along.
I would also like to comment on the power gamers that dislike 'soft skills'

. Every class, PRC, or what have you advantage comes with its own limitations (for example the built in stacking rules). It may seem a pain in the backside, but enforcing any of the drawbacks that may be overlooked for simplicity (i.e. role playing disadvantages for combat advantages) should go a long way to balancing these things out. Look at various ways that skills can influence the combats that these knuckleheads gear for, but never use, such as balance, knowledge (oh yeah, you will be surprised at this one), jump and others. Once the players see how these skills can be useful, they will find they need to start investing those points in other places. Feats and skills with one line descriptions are hard to abuse, but the paragraph long ones often give you the advantage up front to catch your attention, then two or three paragraphs later comes the punchline. After pointing this minor flaw in research out with certain player types in the begining, they catch the hint and make wiser choices....usually.