Roll the lime across the countertop with your hand, squishing the juice free from the lime. Juice the lime. There are some nice two-handled squeezers out there for the task, or just cut in half and squeeze out with your hand. Use a lime half to dress the rim of the glass with lime juice, and dip the glass in a flat dish of salt. Fill glass with ice. Stir lime juice with triple sec and tequila, pour over ice and let it chill a bit.