It all depends on how think the chicken is and what I am cooking it for. If it is really think I will cover it to keep it from drying out. If the chicken has been marinaded with some thing that has a High sugar content. I will cover the pain. The steam will help stop the drippings from getting black and tasting like shit.
If I am Pain frying the chicken. Say like you would if you were cooking breaded chicken then of course you would not cover it. If I was cooking a thin peace of chicken breast for something like a chicken marsala. Then no I would not cover it because The chicken is going to cook fast, and I need to have the lid out of my way well I add the wine,mushrooms, other veg, and what not at deferent times during the cooking process.
For the chicken you want "plain chicken fried in a pan" just heat the pain up to med high heat. Brown the chicken off on both sides. then drop the heat down to med low, cover and simmer till its done.