If you still collect, visit ONCE, and if they don't have cash, ask for a cheque. If they're not in leave a SAE with payment instructions.
Only visit once! If you don't get paid, just add it onto the next clean and leave it upto three cleans. If after three cleans you still have to chase payment; drop 'em once you're paid.
For drive betweens or rural accounts, don't collect, just leave an SAE with payment instructions. If you don't get paid, just add it to the next months clean.
In about 9 years of window cleaning, it is very rarely I've ever been 'knocked' for a payment from a customer; the vast majority are fine; even the 'add it onto the next month' ones.