Remember a sale is only a sale once it has been paid for!
The best way of assuring you do get paid is to assess your customer's ability to pay what is due to you within their credit limit. This is known as assessing the credit risk and once completed you will be able to assess credit terms and credit limits.
Your criteria will vary depending on the assessment's result. For example you would only supply on a cash only basis if you thought your customer were shortly to proceed to insolvency. A different response will apply where your customer's liquidity ratio was improving