When you see something new, ask yourself: Will I use this right away?
If the answer is "No," or even "Maybe," don't get it until you can answer "Yes."
If you're worried about losing it in the jumble, you can: write it down by your computer, bookmark it, or realize that something that forgettable probably wasn't worth downloading anyway.
When dealing with multiple recolors of something, whether it be furniture or clothing or hair, only get one recolor, the one you're going to use right away. No matter what your gut is telling you, you don't need 12 shades of one hairstyle unless you have 12 Sims ready and willing to wear it.
- Clothing recolors should be limited to one or two.
- Hair recolors should be limited to five maximum: black, blonde, red, brown, grey/white.
- Lots of the best hair creators give you multiple choices of each color type (brown, lt brown, coffee, etc). I only download the maximum when I consider the hair a nice, basic style that several Sims would look good with (never when the style is too obvious). Otherwise, I download my favorite color of the bunch and the white version for when they get old. And that's it.
When downloading something new, try it out in the game and see if it still looks as good as you thought it would. I've often gotten hair that looked amazing in the promotional photos but looks just plain goofy on my own Sims. When this happens, always go and delete the files immediately.
There is no point keeping something you don't use in your files, no matter how cute it is.
Even if you have a subscription and want to make sure you can get to those files again after it runs out, put them on a data CD instead of letting them clutter up the custom content panels in your game. I've wasted a lot of time scrolling through hair I've never used but "might one day." And it's really not worth it.