If you don't have a citrus juicer handy, then take your lemons and heat them in the microwave for about 20 seconds. Press a lemon under the palm of your hand and roll it on the counter while pressing down and away from yourself (much like when you are kneading dough). Press the lemon onto a cutting board and slice it in half lengthwise. Squeeze the lemon into a bowl. Try to get as much juice out of the lemons as possible.