A credit check will typically show a score (out of 100) and a maximum credit that any supplier should allow them. I would be wary of any score less than 50%. The reports will also give details of any court judgments (i.e. have suppliers had to take legal proceedings for payment) and possibly the number of days which the average supplier can expect to be paid in. They are generally easy to read and interpret.
Cheers
Whirls