How can I be a good client?

As a company, how can we be good a client of a software engineering company? We want to do everything in our power to support them in the development process.

I'm asking this because we had some failures in the past. And we can't put all the blame on the software contractors. It looks like to achieve a good software, there must be a very strong cooperation with the software house.

Any good resources or books that you guys can suggest?

Thanks so much.