Masking tape will leave a residue, but will those white little round labels used for pricing at thrift sales also leave a residue over time? I'm trying to mark on each piece of fabric its size, but not sure the best way of doing this. Any ideas? Thanks in advance for all your insightful answers. :)

I use a safety pin and piece of paper:)

painters tape will not leave a residue.
i use post=its to mark mine

I either write in the selvage or use a 1" x 1" post it & staple it to selvage

What about individual baggies with sizes written on it and place all the same size together?

They sell pins with letters on them Nancy's notions I believe

The "super sticky" post it notes stick OK, as long as you don't tug them around too much. But I'll watch this topic, for sure

I make small fabric flags and staple them into the selvage edge or along the cut edge. You can find stainless steel staples that resist rusting. You can also use the sequin pins - I don't because I always seem to get stuck and bleed all over the fabrics. Damn blood thinners.

Edited to add - on my fabric tags, when I mark the length I also add WOF or the exact width if not full.

Very nice ideas...I never thought of marking my fabric...I just keep a notebook/journal and use a baseball card holder in my journal to keep a swatch of fabric with name and dimensions.

Yep, me too.... or if it is several small pieces I want to keep together, I use a zip lock baggie and write on the bag