Burpees are a full-body exercise you can do anywhere without any equipment, so they're great for eliminating excuses. (No gym membership? Short on time? Snowing outside? Burpees are having none of these excuses.) Plus they're effective as hell. Find your baseline by timing yourself for five sets of five with as much rest as you need between sets, then double that time to determine the number of days it should take you to work your way to 25 continuous burpees (if it took you 12 minutes, for example, you've got 24 days to reach your goal). Aim to do your 25 burpees five days per week, working up to two sets of 10, plus one set of five by the halfway mark, then decreasing rest between sets until you're a bona-fide burpee master.