Here's my method, works every time (if the plane is capable). Climb vertical to a high altitude. Chop the throttle, and as it slows down, but before it stops, kick in right rudder then neutralize it, just to get the nose over to the right, sort of like the start of a hammerhead. Rather than finishing a hammerhead though, as soon as the nose is level with the horizon, give full power, full down elevator and full left aileron, hold it briefly to let the spin establish, then feed in full left rudder. You'll be spinning down at this point but not completely flat. Now start slowly taking the left aileron out of it, still holding full down, full power & full left rudder. You may not be able to eliminate the left aileron completely, but you'll see the spin go flat (and if you remember where the aileron input was, be able to gos triaght to it the next time). It should be a very flat KE spin at this point, and dropping straight down. When you get it right, they come down fast, so start high, and be prepared. Most will exit easily by nuetralizing the rudder and elevator while maintaining full power, then rolling left for upright or right for inverted flight. Tthe only real trick here is timing it right so the plane is going in the direction you want it to when it stops spinning. Good luck. It isn't hard once you do it a couple times.