I think the number one thing is you have to give people a reason to pay. Being useful is of course the first step, but people also want to feel they're getting something "extra", they want to feel like it's a transaction, however bad.

One of those things can be to provide a very clear road-map tied to donations and then follow up on it. That's what so powerful with these crowd funding campaigns. People feel like they are making a difference though at times they are essentially buying something.

I don't think you necessarily have to "compromise your values" either. You're probably already limited by money, so add some planning and just be honest about it. "With this amount, this will happen" etc. As always of course "under-promise and over-deliver".

That's mainly for individuals though. Companies are somewhat the same, but they want things that fit into their budget.