How much time can you wait and what do you want to spend? You just missed the summer sales, but if you wait a little Labor Day should bring up a few sales which might save you money. Also, if you're one of those budget freaks who refuses to spend more than $10-25 on a pair of pants, well you get what you pay for. $25-40 can get you some solid clothes, especially if you wait for a sale, and if you go $50 and up you should be able to get something real nice, although at that price range you should probably get something more adventurous and stylish instead of a plain old pair of khakis. Stick to natural fabrics like cotton, wool, and maybe linen if you're in a warm climate, although a pair of stretch khakis made of 95% cotton, 5% lycra or something may work well.
As for pleated v. flat front, if you're young and not really big, you should go flat front. They've been in style long enough that they're acceptable everywhere, and in fact pleats on non-formal pants are often considered ugly and dorky (especially with the ladies heh).
Regarding brands, I don't know your price/style range, but I definitely think you should avoid budget brands like Old Navy, Dockers (I once heard someone put it well by saying that Dockers were only for people who had their pants bought for them), Gap (it's gone downhill), and any of the half-assed department store brands. On that same note, stores like A&F, Eddie Bauer, and AE may be popular and somewhat more expensive, but they have a really poor reputation for quality and durability. Off the top of my head and not knowing any more info I'd recommend Banana Republic, Structure, Polo, DKNY, Kenneth Cole, and maybe Brooks Brothers, but you should wait til the bigger sales are going on because you can pick up those pants for the same price as a pair of Dockers or Old Navy's.