I did a copy and paste on a set of generic "terms and conditions" and only give credit to carefully selected clients usually up to 21 days, that way I can 9 times out of 10 get the cash before I need to pay my suppliers who normally work on 28 days. I clearly state the goods remain property of my company until paid in full. In the past 18 months I have only had to chase 1 customer after the payment due date and that was a so called "mate"!!!
Late payment is based on interest paid cumulatively at a % above the banks base rate and is clearly stated. Fortunately my wife keeps me right when it comes to vetting credit customers and they tent not to be individuals.