I don’t. Ever.
I will give you money if I can spare it, but the second it leaves my hands, it’s not longer mine. If you choose to give me money in the future, great. If not, shut up about it. Don’t tell me you’ll pay me back because you don’t have anything of mine to pay back.
Edit: If this sounds strangely hostile, I just had a friend tell me for the fifth time, “They haven’t forgotten.” And… “They just need to wait until payday.” I’m about to start forcing people to sign, “IDON’TOUs”