The thing I love about tri-tip (besides the fact that it's a bottom sirloin cut - my favorite primal cut) is that it can be cooked so many different ways and turn out great. You almost can't go wrong with it.
Typically we season, then put the cold steak on the grill at 250° - 275° and cook indirect. The cold steak takes longer to warm so it takes on a little more smoke. Cook to an I.T. of of about 132° - 133°, pull and rest.
By the time the I.T. peeks from the carryover heat we end up with a nice medium-rare in the center (which the rest of the family likes) and a medium on the outside edges (which I like).
I just wish Tri-tips were more readily available around here.