ORIGINAL: CGRetired
Get a board, put an engine mount on it, clamp the board to a saw horse, attach a fuel tank behind the motor, a wire to the throttle, start the engine, and break it in.
Can't get much easier and cheaper than that. I don't know about the best, but it works for me.
CGr.
This is pretty much exactly what I did and very cheap to do. The only thing I do different is that I mounted an old receiver and battery to my board and I can let the saw horse sit a distance from me and use a radio to control throttle. Works super good!
I was running some larger engines and I just had to put a weight on the end of the sawhorse so it would not pull away [X(]