> Have frequent and early deliverable dates.
Both of these things are extremely difficult (if not impossible) for experienced software consultancies to know up front, let alone the crowd looking to outsource. More importantly both figuring out what to build and knowing when those things are deliverable have, in my experience, required the involvement and input of the developer.
Telling an outsourcer "do X for me", where X isn't a well defined thing (ie. run a warehouse, manage windows servers, etc) is going to be a disaster. What does "add a shopping cart of my site" mean? Do you want to figure out sales tax for various jurisdictions? Do you need to to interface with the German banking system? Is there a configurator?
If you treat an outsourcer as a partner in development and participate in that process, you're either going to get a result that makes sense, or you'll figure out that the process isn't working out and terminate early.
Bingo. This is why you need in-house dev talent for creating bespoke applications.