Often it's a matter of luck. You can sometimes come across the 'deal of the century' and sometimes nothing.
My feeling is that local business clubs are best for the cleaning trade. Usually a small (say £50) annual membership and a chance to meet business people from your town. Personally I avoid the £500 a year breakfast clubs which place a lot of pressure
on you to turn up regularly and give referrals - not always easy to do.
Never 'push' your service. Just chat to as many people as you can and give out plenty of cards.
Good luck.
Laurence