How many times should I cut in?
How many times is mostly dependent on the quality of the paint and the particular color. 

You want to do it enough times so that it matches the rolled-on areas. 

There is no 'one way' to do this, but typically I cut in first, then roll, then touch up as needed.

I don't bother with tape. It's much faster, less messy, and (over time) more accurate to get the hang of using a good brush and cutting in manually. The tape rarely works as well as you want and adds a whole lot of time to the project.