Break the project up into clear deliverables. Charge for delivering, not for the entire project, and not by the hour. At every step the client can see real progress and you have something tangible to bill for.

I have freelanced for 15 years, never had a client refuse to pay. Big companies with bureaucratic payables systems can take time to pay, you have to anticipate that, typically net 30 days.

Retainer arrangements also work well if you have a long-term relationship with the client. You get into their payables system as a recurring fixed cost, rather than an irregular invoiced amount.