Similar to my bead collecting post, I'll now talk about what to look for when adding to your fabric stash.
Fabrics are more difficult to store than beads because they can become home for insects (especially wool) and if they become wet, they can mold. Velvets are difficult to revive once they have been crushed. So above all be sure you have a place to store the fabrics you buy.
Trims: These should be stored rolled or on cards, and like beads, it's difficult to have "too many" trims so be frugal.
Decorator fabrics are best stored on rolls. Quilting fabric is fine folded.
Always buy fabrics you love and intend to use. Don't get caught by the trap of "Well, I don't love this but it's really cheap." Buy things you intend to use and you'll probably end up using a lot more fabric overall.
Make sure to buy not just beautiful fabrics but utility fabrics as well. You will need a lot of interfacings, linings, and maybe even some canvas or underlining muslin or osnaburg as well.
Make sure you have colors that look good together from which to choose. Always pat attention to the weight of a fabric: Will it hang well? Will it last a long time under the intended use?
Pay attention to what fabrics you actually end up using vs what you have bought. If you have too much of something you don't usually use, try to offload it so you can have room for what you really need.
Hope this helps someone!
--Pam