How can I stop the delivery of mail for old residents at my current address?

i toss most of the mail that comes for the guys who used to live at my place over 5 years ago, but every once in a while a "real" piece of mail pops in and i always just cross out the address and bar code and write return to sender, and pop it back in the mail.

I also toss out most of the mail, but when something looks important, I do as urban_mermaid above does with "Return to Sender" and cross out my address. Additionally, I write "Addressee no longer lives here."

I have done the same "return to sender" thing that Carla described above. Another thing I've done is sign up with Green Dimes (greendimes.org). They will stop the junk mail even if it's addressed to past tenants.

One thing that my apartment owner did that was kind of helpful is he provided me with pre-printed "please forward to this address" labels for the former tenants who were still receiving mail here. It made it really easy for me to just paste on the label with the new address and pop important-looking things back in the mail. That said, it certainly doesn't stop the new mail from coming. I do think that Greendimes (as Katie posted) has also limited the junk mail. But I do occasionally get stuff for the old tenants.

You can also go to the post office and fill out a form stating that particular names are no longer at your address. A bit of a pain but it stops it once & for all.