Couple of ways to do this. One, you pick a font style and you hand animate each letter, using one of the many techniques for After Effects Write-on. I had to do this for a series of videos year ago, ended up creating animations for every I character I needed(entire alphabet, numbers, symbols), rendered them out, would place them in a precomp, spelling out each thing I needed. Move that precomp into a final comp and time remapping to get it to match the audio. Very time-consuming, but that’s what the client wanted.
The other way is to buy a package of fonts that are already animated, like Animated Fonts
Johnny Cuevas, Editor
ThinkCK
“I have not failed 700 times. I have succeeded in proving that those 700 ways will not work. When I have eliminated the ways that will not work, I will find the way that will work.”
—THOMAS EDISON on inventing the light bulb.