It depends
It really depends on the lake. Most lakes around here don't have a limit and some consistently produce larger crappie - like GLSM. Our closest and favorite lake has tons of small crappie and if you're willing to clean them you can fill a cooler with 7 and 8 inch fish.
When we first got back into fishing, we kept anything over 8", but the occasional 7.5 snuck in there, too. As we improved, we kept moving up the size. Absolute minimum now is 9, but we're real close to changing that to 10. We only keep a half dozen fish for the two of us anyway, so we don't need to keep the little ones.
I clean the small ones just like the others - scale and filet. We like the skin on. It's not a bad idea for some smaller fish to be taken if the lake's getting overrun by dinks.. They're tasty - it just takes more of them to make a meal. - Roberta
"Anglers are born honest,
but they get over it." - Ed Zern