Use a plastic collander in a microwave safe plate to cook your ground beef. Cook 1 minute at a time and stir and break up chunks after each minute. After it is cooked all the fat will be in the plate and you can put the meat in a skillet to brown it.
Do not rinse beef in your sink!
1. Because the grease will clog you sink drain.
2. The hot water from your faucet is not hot enough to melt the grease, it actually congeals the fat to the meat!
I was taught this by a licensed dietitian years ago and I use it all the time.