USPS Mail Advice: How do I get rid of mail of former tenants?

I live in an apartment in lower California. I keep getting what seems to be 3 real peoples names and a spam name mailed to my house. The spam name is “LittleJohn Jihad” just thought I’d share that because that’s funny. But anyways, for the other 3? What do I do? Just put it back in the return box? Or should I write “No longer lives here” or something like that?

Thanks!