Duck-Under Set-up for the Flying Triangle
this is my favorite way to hit the flying triangle. It looks difficult, but it's actually quite easy; I honestly think the hardest part is hitting the duck-under. Just takes a little practice and good timing. Once you get it down it's near impossible to see coming.
YouTube - flying triangle off the Duck under
People generally expect a suplex, takedown, or attempt for hooks after the duck under, and the general pre-emptive movements they make to defend those techniques makes the triangle even easier to hit.