How to chose the best transition type? That's a tough question. It depends on where you are applying the tweening. As a rule of thumb, I usually use easeOutExpo or easeInOutExpo on movieclip sliding and transformation (or easeOutBack or easeOutElastic when I want something extra-fancy); I use linear transitions on all color transitions, including alpha changes, and on all sound transitions. Be careful, though, to take animation time into consideration too - if you do a easeOutElastic transition in 0.3 seconds, you won't even notice it. So try different ammount of times until you find the value that fits your animation best.