The small print written on bottom of invoices of invoices, for example.
But they are more than that. They help you set up profitable and sustainable deals with your customers - you get paid on time, and customer isn't surprised by sudden changes in plans or service.
It is also good business practice to send polite but firm email/call/mobile notification as soon as any payment is due.
Other ideas:
- Upfront Deposits, balance on delivery
- Invoicing every week/fortnight (useful for freelancers instead of waiting for 30 more days after end of work)
- Maintenance plans (e.g. air conditioner purchases)
- Annual increases (e.g. cable)
- Incentives for referrals (e.g. Dropbox)
- Discounts for timely payment