For myself I won't do a second clean until I've been paid for the last clean. Though to be fair that isn't a hard and fast rule, some customers you get to know and their non payment can be an oversight (ie, not sending a cheque in the post) and I will let it pass one month.
If I have their phone number I will ring them and ask for payment, either to leave it out in an envelope or post it.
Those that are a pain to collect if you have cleaned them when they are not in, then once I have got the money out of them I only clean them if they are in, I'll call a couple of times as that area of the round falls due, but if I can't catch them in then I stop calling.
If they ring and ask where I have got to, I tell them that due to difficulty in collecting I could only clean them if they are in and can pay me on completion. In the past some have said, "Oh but I work all the time, I'm never in during the week."
When I politely point out that they don't send a cheque, even after repeated requests, they usually say they will in future. If I am in a brave move I'll tell them sorry, no can do and tell them I'll pass their name on to another cleaner.
I usually bottle it though
And tell them no problem, but then don't bother calling on them
Yeah I know, bad of me, but sometimes it just isn't easy to tell someone they are a crap customer
With those that say thanks but no thanks this month, it's raining/going to rain/windy/not dirty and so on, well, they become 'if in' accounts and it then depends on how good the account is, and how well it pays as to how often I call back...........and that has nothing to do with the fact she may be drop dead gorgous and looks really interesting on a cold or breezy day when she answers the door
Or perhaps she's just pleased to see me
I am never rude to a customer, even when they are doing the equivalent of an audition for 'Customers from Hell'. I never call back on them of course.
Customers are funny creatures, they all seem to have differing views of what constitutes window cleaning weather, but if you can't rely on doing them every month then let them fade away, they aren't worth the hassle............unless they are female and fill out a tee shirt in a really interesting way
Ian