If you want to build muscle, you'll need to do multiple sets of each particular exercise with short rest periods between sets. The short work-to-rest ratio will be uncomfortable, but it'll pay off.
Short work-to-rest means that the time between exercises is minimal so you end up getting more work done in a shorter amount of time. It'll get the fat-burning hormones in your body working overtime. Start by doing six to eight repetitions of six different exercises with only 30 seconds rest in between [source: Morton]. Repeat the entire circuit three or four times. You'll feel spent, but your body will work quickly to restore those muscles, leaving you looking buff.