Abandoned Cart #2
I like to send the second abandoned cart email 1 day after the initial one goes out. You don't want to follow up with the customer every single day but in that initial period right after they abandon, you want to start out more frequent, and then begin to reduce the frequency over time.
This can be a good time to begin to think about introducing a discount, although to be on the safe side you could always wait for a 3rd abandoned cart around day 3.
If you do introduce a discount, I'd recommend that you only make it valid for 24 hours or 48 hours - some kind of window that will create some urgency and also prevent people from trying to game the system by storing up a bunch of these for the future.