After reading J.D.'s post on the money you can save by buying generics or store brands and skimming most of the comments I thought about my own decision making process and thought I'd chime in. First of all, I agree wholeheartedly with the people who argued his methodology was flawed because he refused to consider sale prices for brand name items, even those on sale during the week when he conducted his study. If brand name items are cheaper, they are usually the way to go. Aside from that circumstance, I've concluded that most of my consumable purchases fit into one of three categories.
For most items, generics are fine. A quick look around my bathroom reveals generic mouthwash, dandruff shampoo, salicylic acid astringent, maxi pads, and anti-itch medication for those pesky mosquito bites. I don't think I've ever bought name brand medications when there was a generic equivalent available, and my fridge and pantry are usually stocked with generic milk, pasta, oatmeal, etc. I'm definitely in favor of trying a generic if it is available.
For a few items, I stick with name brands because I've yet to find a generic option that isn't pretty bad. There's a bag of shredded Parmesan cheese in the refrigerator that looked convenient but is actually nearly tasteless. I gave up on cheapo deodorant years ago after trying a Suave version that was very ineffective at fulfilling its sole purpose. For all I know, it could have been reformulated several times since then, but since deodorant is nonperishable and I'm not tremendously picky about what kind I use, I can buy brand name whenever it is cheapest so it isn't worth experimenting with generic again.
For a handful of items, I've concluded that a specific brand adds enough value to be worth the extra cost. All frosted shredded wheat are exactly the same from what I can tell, but once in a while when I want oat cereal, I want it to taste like actual Cheerios. I know it is largely a matter of conditioning, but the other kinds just taste off somehow. It's a small indulgence. The same goes for conditioner: I've tried lots of things, but nothing leaves my hair quite as soft and shiny as Pantene for curly hair. So for these items I keep a close eye out for sales and coupons, remind myself of the trade offs associated with spending my money on them, and then try not to worry about it if I decide to go ahead anyway. That's all subject to reassessment if I ever find myself in need of a stricter budget, but it seems to work for now.