Be paid or don't work.

I am so deadly serious - do not continue working if your invoices are late.

You don't have to be a jerk about it, just explain to your primary contact that you need to be paid and you pick up tools again when the money has arrived.

BUT it is on YOU to properly negotiate reasonable payment terms. And if you don;t know or don't trust the client then require payment in advance until a stronger commercial relationship can be settled in. Do not be a baby - go research business contracts and payment terms.

Do not be afraid to lose business from companies that are squeamish about paying you - in fact actively avoid such companies.

Sadly this is true and lesson anyone who has worked freelance has probably learned - either that or I'd wager they no longer do freelance.

Its easy to say don't be afraid to lose business, but when you're starting out, the economy is rough or all you have are the one or two clients, that's a different matter entirely.

One thing I've learned is that you always have to do the leg work, you can't assume someone will do the right thing or keep their word.

Develop a system where even bad clients, can't do too much damage i.e. upfront deposits, milestone-based payments. You have to control cash flow risks, if you are gonna take risks know what risks you're taking and when to get out.