Do you do good work?

If you do good work, give them what they want (and sometimes more than they ask for) and they've agreed on the price then don't hesitate to bill them. Once they've agreed you've delivered what they've asked for then bill right away.

I'm a technical consultant myself (Diablo iii Gold). I've been doing this since 2001.

I wouldn't expect to get paid for something that I wouldn't be happy with myself.

If you are happy with what you produced then they should be too.

It's hard to estimate sometimes because most of the time I'm being asked to do something that hasn't been done before. Always be optimistic but pad the estimate within reason. It's easier to tell your client that it took less time and is going to cost less than it is to tell them it's going to take more time than you though and it's going to be more money.

Don't take a job for less than what you think it should be (Diablo iii Gold). You won't be happy with it and the client won't be either.

Those are just a few tips I've learned over the years. Hope it helps. :)