The easiest way to test for how done your steak is, is to press on the meat with your fingertips. Press on the meat here and there while it cooks, and compare the feeling of the meat with the following finger test. You’ll get better with practice. Please note, this method only works when cooking steaks, and will not work with roasting joints.
Open the palm of your hand. Relax the hand. With your other index finger push on the fleshy area between the thumb and the base of the palm. This is what raw meat feels like.
Press the tip of your index finger to the tip of your thumb. The fleshy area below the thumb should give. This is what rare meat feels like. Open up your palm and compare raw to rare.
Gently press the tip of your middle finger to the tip of your thumb. Feel the flesh beneath the thumb. This is what medium rare meat feels like.
Press the tip of your ring finger and your thumb together. The flesh beneath the thumb should give a little more. This is what medium cooked meat feels like.
Gently press the tip of your pinky and thumb together. Again feel the fleshy area below the thumb. It should feel quite firm. This is what well done meat feels like.