Save your change
I save the change I get, put it in a piggy bank, and every couple of months count it all and roll it up. It's so simple, but I don't think a lot of people do it anymore.

Get a 2nd savings account
Preferably a high-yield one, though those are harder to find nowadays. Keep all extra money in that account and let it grow. I have one that I completely ignore, except to add to it, unless absolutely necessary.