How can I best clean the print bed after a print?
If you are printing with ABS (or PLA), acetone will dissolve it.  Simply pour
some on the bed and wipe it off (beware, acetone can damage beds that have a coating or a plastic sheet over them, be sure to test this first).

Heating the bed back up may make the plastic softer and easier to
remove.

If you are using tape on the bed, you could remove the tape to remove
the plastic stuck to the tape.