Many say that we should squeeze our suppliers, pit one against the other, find out who is the most desperate to get the business, then pay late.
This is of course self-defeating.
The more you squeeze, suppliers will find a way to make money. Either they will deliver late (to cater to someone else first), deliver inferior quality too late for you to reject, or simply accept your job and do it only if they get no other business.
The game two of you play is a no-win game.
Treat your suppliers as partners with respect. If the cost is too high, work with them to revise your specs or deadlines. Understand their problems. Be clear about your specs and don’t keep changing your mind.
Now you have a win-win game.