How can I practice different expressions for my characters, instead of having them roll their eyes and scowl?

Usually, you should only have them do something every few paragraphs. It's very distracting to do it each time. The reader can usually tell who's talking if you do it every other time. Especially if each character has a unique "voice". For example, in my story, one of my characters says the word, "like" every few words. It drives the other characters crazy, but I usually don't need to explain who is talking. Another one of my characters uses big words they don't understand. Another one stutters.