When you are cooking a piece of meat the best way to tell the degree of doneness is by touch. This takes some practice. If you touch the meat before you begin you can tell how much give there is against your finger. As the meat cooks the proteins bond and the meat becomes firmer and less rubbery.
After about 5 minutes of cooking at high temperatures a steak will begin to firm up at the edges first. Touch the meat frequently and you can feel the difference as it cooks. (you can do this with tongs if your fingers can’t take the heat). When the meat is about 25 – 30 % firm around the edges it is rare. A little more and it will be medium rare.
This takes practice but you’ll have a good time and remember that Julia Child told us that it’s OK to touch the food – just be careful – it’s hot.