Power drills come in 3 sizes; 1/4, 3/8, and 1/2-in. Size refers to the largest capacity of bit that will fit in the drill's chuck. 3/8-in. drills are the most versatile. They're powerful, yet light enough to easily hold and manage. Larger bits can drill bigger holes, so 1/2-in. drills are best for big, heavy-duty projects. Drills with higher RPM ratings (1200-rpm or more) are better for boring smaller holes into wood. Lower speed models are better at making larger holes into metal.
A 4-ft. T-square for drywalling can come in handy for other projects. Besides being helpful in drywalling, it can be useful when laying out patterns or cutting on full sheets of plywood or particle board. The square is accurate, stable and will give you a full 48-in. straight line. Some newer versions come with a head that can be adjusted to various angles, then clamped in place.