Simple PowerPoint in After Effects

Primarily I want to know the simplest way of fading out  elements/layers  and timing this to animated text.

I want to do it in the style of a powerpoint presentation but without the clicking - so time limited slides.

If I were to Pre-Comp things then I could synchronize things more easily.

Now how would I get things to fit in and out?

Would I just limit the layer's length to how long I want it to last? Or would I just use Opacity?

There are so many different options - could you guys suggest the easiest way of doing it please

Thanks very much.