The surest way to know if your meat is cooked properly is to test it with a meat thermometer. But if you find yourself without one (as I did at my summer vacation rental), you can find an easy guide to meat doneness, literally at your fingertips.
Hold your hand in front of you, palm up. Keeping your hand relaxed, touch your thumb and index finger together. Now press the fleshy area under your thumb with your other hand. That is what rare meat feels like. Press your thumb and ring finger together. The fleshy area under your thumb now feels like meat cooked medium. Press your thumb and ring finger to see what medium-well feels like and thumb and pinky for well-done.