It depends on the results / goals you are looking to achieve. If you like full, body workouts though, work the three, general muscles - Quads, Chest and Back. Working these three will involve the other muscles, which assist (i.e. triceps, biceps, calves, hamstring, etc.) Try a circuit routine - 8 to 10 circuits - 1 circuit = 20 repetitions of a chest exercise, 20 of a latissimus dorsi and 20 for quadriceps. Good recommendation exercises, for each muscle group are - Chest area (anything involving a press forward motion using arms - bench, machine press, push ups, etc.), Lats (anything involving a pull motion - wide grip pull downs, close grip pull downs, rows, etc.), and quadriceps (squats are the best; especially standing on a bosu ball.) Do each muscle group, 20 reps and continue to the next muscle group with no rest. When you complete all three (chest, lats and quads) you completed one circuit. Rest for about thirty seconds, then do another. Do eight to ten circuits. Afterward, three sets of abs and cardio if you have the time / energy