If the fish is small or there isn't a lot of line out, you can just keep the line coming from the first guide in between your index and middle finger. Squeeze the line with those 2 fingers if you want to apply some drag, and use your free hand to strip line in.
If the fish is larger, or you have tons of line out and you want to fight the fish from the reel, assuming the fish hasn't taken all of your loose line out,
keep the line coming from the first guide in between your index and middle finger as before
have the line coming off the reel in between your pinky and ring finger.
This will allow you to control the fish with your dominant fingers, while allowing you to reel in the loose line with your free hand and feeding it through your less dominant fingers so that it goes back on the spool evenly.
Alternatively, you can pinch the line against the handle instead of running it between 2 fingers.
This should help you avoid holding the line between your lips.
This is what I do, self taught, don't know any other way.
The main issue with lost fish I assume is a result of not keeping tension/pressure on it while your trying to deal with a mess of line.
Done correctly, it should look like this: