Is there anything else for a girl on her period to do for her not to leak?

Assuming you mean leak as in NOT swimming.

If the flow (heaviness) is really heavy, you could either wear overnight pads, tampons and pads or 2 pads. You could also wear two pairs of underwear, so if you do start to leak, you'll feel it and have time to save yourself.

It really is up to the woman to decided how she will deal with her period.