First of all, you'll want to make sure to use a ripe lime. When the lime feels hard to the touch, it's not ripe enough and will not give you much juice. A ripe lime is soft but it does have resistance. If the lime is too soft and the skin starts to wrinkle, the lime is over-ripe. Make sure to either let the lime warm up on the counter to room temperature or pop it in the microwave for 10-15 seconds to warm up. Then, gently roll it on the counter with your hand on top. Warming the lime and rolling it will yield the most juice.