It seems like drawing in your own text can be best sometimes, but overall you want to center your dialogue within the speech bubbles. Treat the bubbles themselves as though they are frames, and the dialogue as if it is the artwork within the frame.
"Making Comics" by Scott McCloud is a FANTASTIC guide if you wanna read more on the subject. :D
Anyway, THIS IS GREAT! Lupin and Jigen are the best aaaaa