I just bought some, but there is no size indicator on them! So, if you have more than one pair, how do you remember which is which?
well sometime you can tell just by the difference in size but the best -more sure method would be to pick up a little gauge thing- not sure what its actually called but it has a row of little holes with the size printed above it. you just stick the needle in question in the hole and the one that fits it is it' s size. you can be sure cause if you try to stick it in the one smaller it just won't fit. they usually also have a spot to measure your gauge when you swatch. i hope that makes sense.
My bamboo needles have size guages on them, but if they didn't, I'd be inclined to mark them with a dot of nailpolish, with one color for each size. I keep all of my needles together in a zippered pencil case, so I'd probably then attach a key to the case.
ETA: Using different colored Sharpie markers would also work, I would think.
All my bamboo needles the size is laser etched in the side. I got a knitting accessory kits and it had a plastic needle gage card and I was wondering why I would need that if all the needles are marked but now I know they aren't all marked!
Scarlett , DH Boris , DS 1/29/08 Julian DD2 6/7/12 missing our DD 1/06/06 Sonja and MC @ 9 wks 11/18/06 Satchel
IMO having a knitting gauge is indispensable. I have a large collection of different brands and types of needles and the printed size doesn't always match the actual measurement, I have some Boyles that are really off. Plus I have some antique Canadian/British needles which have a totally different numbering system, to the US/metric sizing. I always double check the gauge on those ones.