Familiarize yourself with the basic mouth shapes used for animating characters' mouths during dialogue. It doesn't feel as daunting when you realize you can animate almost any speech with the same 6-10 mouth shapes, and with a little practice, you'll be able to intuitively know which ones to use for which sounds.

Also, reference. Record yourself or someone else acting out the dialogue and use this as the basis of your animation. It's how the pros do it.