Why do you need software outsourcing?

Let's start with why. If you have enough budget there is no need of outsourcing.

Outsourcing is to save money. If you did not save money by outsourcing, that means you may have chosen the wrong partner.

How do you outsource you software service?

The most important part software outsourcing is to find the right partner.

This is a little difficult, because we are from different places and different culture. However, there's some tips for reference.

Get trial project, to see if the company can do good job.
Try those company who work hard, like Chinese, they maybe a little expensive, but they work really hard.
Take experience into account, those who survived from fierce competition shows their good project management and quality control ability.

If you want your outsource team to be efficient, here's some tips for reference.

Set the rule first. Work flow, code standards, quality acceptance etc. those need to be discussed before coding.
Do MVPs. use some tools to draw the prototype and requirement, to make the requirement clear is the most important key of saving time and money.
Communication everyday with the outsourcing team, to make sure everything is under control.
See what the have done rather than what they say, because some team can make good documents but bad software.

That's some rough reference for you to consider of software outsourcing.