I buy online special fabrics that I know I won't find around here - Beautiful Christmas collections, Eric Carle themes, Dick and Jane, etc.
When I am shopping for fabric I take a sample book with me and in this sample book will be swatches I already own. EXAMPLE: - I was collecting roses and rose fabric for a while for an elegant log cabin and with just a quick comparison I could see if I should buy it.
I also know what types of what I call "fillers" I will use... Tone on tones, mottles, certain colour groups... never pass up a good golden yellow ! It WILL get used! So if I see something I know I will use I get it.
And then there is the "OMG" factor. Don't know what I will use it for but I just can't leave it there for someone else to buy because I KNOW what they won't love it and appreciate it like I will!
AND having said all that... when I am looking for that last piece for a project, I can NEVER find what I want!!