Plastic worm fishing can be a very effective tool for catching largemouth bass, especially in the colder months of the year. This is true due to the fact that the water is colder on the surface and the bass tend to bottom feed much more and remain suspended at depth for larger periods of time. The main thing to keep in mind is the way to catch any fish is to pay attention to what is already happening in their surroundings and imitate it.
While learning how to it is imperative that you remember there are too many variables to explain to anyone. Most of what you learn is going to be from the experience of casting a line and actually fishing. That being said, everyone has to start somewhere if it is a thing they want to do, so starting with the basics and how to choose the correct baits is a very good beginning.
The three most important things to decide when fishing with plastic worms are: 1.) the color of the worm, which needs to be chosen for the light availability (the darker conditions due to lack of sunlight or cloudy water conditions, the darker the bait should be), 2.) the size of the worm being used (the darker and warmer conditions are, the larger), and 3.) the presentation of the worm to the fish should mimic the activity of the fish. If the fish are not active, choose a larger worm and fish it slower. If the fish are more aggressive, or if you see a feeding trend happening, match it up with a larger worm and fish it much faster, and hold on for some fun! Plastic worms should be cast out far and allowed to drop to the bottom before beginning the harvest. With practice you will actually learn how to retrieve a plastic worm without having it snag on everything and get hung up!
While it will take some time to learn everything that can be taught about fishing with plastic worms for largemouth bass, with enough patience and practice it will be well worth the effort. Every fisher person has his / her own favorite bait and way of fishing, but a beginner needs to try his / her hand at all of them in order to find the one that is right for them!