I was working on a Motion issue today and thought I would share a few tips that help me set up a Motion Analysis:

Mate all components into their initial position.
Components are expected to move (obviously!!!!) so generally, you want to be able to drag the assembly (in SolidWorks) through the motion you expect to achieve in SW Motion. Once this is done, add a couple of extra mates to lock the assembly into its desired initial position. These can be suppressed within the Motion analysis but they are always there so you can get back to where you started.

Position the model in the graphics window as you would like it to appear in you Motion analysis.
I typically position the assembly as I would like to see it and then create a specific view just for Motion. To create a new view, hit the spacebar to bring up the Orientation View list and select New View which is in the upper left hand corner.

Do these two things before creating the Motion study. It can be tricky to move components or get the appropriate view after the Analysis is created so doing a little pre-analysis footwork can save some headaches.

Start with a simplified version of your assembly.
If dealing with a complex assembly, it can be tough to wrap your head around everything necessary to get everything set up properly within Motion. When possible, I will suppress components, get the partial assembly to run properly, and then reintroduce components. This isn’t always possible but can be very helpful when it is.