Juicing citrus doesn't have to be an exercise in frustration, provided you have the right tool and the accompanying know-how. When working with a few lemons or limes, a citrus press ($16) is the way to go. Not only does it use leverage to eke out every last drop of juice, but it also strains out the seeds and minimizes your fingertips' exposure to citric acid.
Here's the important part: while it may seem counterintuitive, you should always insert a halved lemon or lime cut-side-down when working with a citrus press. If you use the same gadget with a lemon or lime cut-side-up it'll be harder to close, will squirt juice all over the place, and won't be as efficient. Press the handles together firmly until the tool has extracted all the juice. It's that simple.