We use a system where we color/leg code for year. So all the hens born in 2013 are blue/right leg. Last year they were green/right leg. Next year they will be yellow/left leg since I still have some yellow/right leg hens from 2011. We use the bandettes that have numbers on them.
I don't bother...
Size 9 should take you pullet through adult as long as you aren't marking Jersey Giants or another very large-legged bird.
Sigh, I have a bunch of size 11 bands and I just found another one on the coop floor this morning. Size 11 is just too large for my pullets. I was just thinking today that...
Get some small spiral bands. They don't fit tightly around the leg in the first place, and If the bird grows, the bands have some give to them.
Here's a link so you can see what I'm talking about, but you may be able to get smaller quantities elsewhere...