As part of your regular leg workout, you should always include a calf program. This small muscle at the back of the bottom leg is often forgotten because people get too caught up in only working muscles that are aesthetically pleasing. Since this area of the body is often not noticed, that means it gets neglected. The problem with this is that these muscles play a major role in any movements you do that involve standing so it is critical to include them.
A well rounded calf program should include both resistance exercises and stretching exercises. As this muscle has slightly more slow-twitch fibers, enabling it to be more endurance in nature, you can perform a few more reps than you do with the other muscles in your body. A good range to aim for during your calf program would be 15-25 reps. Take note though that there is no need to bump that up to fifty or one hundred reps. If you are doing that many it would be much smarter to simply increase the resistance instead.
Try and also ensure that you are doing a few different varieties of exercises as well. This muscle will adapt very quickly to the stimulus you place on it so you should try and shock it a little each workout you do. This could come in the form of a different exercise, a different weight, a different length of rest period or simply doing them in a different order in your workout. If you really want to challenge them, try super setting them in with all the other leg exercises you do. This would mean that right after you do a set of squats, go do a set of raises. Then go back and do a second set of squats followed by a second set of raises. Continue doing this all throughout your workout and by the time you are finished you will be sure this small muscle has received its fair share of work. That would be a very intense workout in nature however, so remember to allow for enough rest afterwards and only perform it on an intermittent basis.