I'm assuming you're looking to add size? If so, you need to hit those suckers hard and often. Calves are notorious for not reacting to training for size. I've got a couple tips to help;
The first thing is to NOT bounce when you do calf movements. Let the calf stretch completely, wait for a second or so, then push the balls of your feet out hard and squeeze the contraction. After squeezing, slowly lower back to a full stretch. Most people bounce through their calf work and they aren't really getting much from it.
Whenever you have a specific muscle you want to grow, you need to hit it often. Luckily, calves are quick to recover. I'd say you could hit them as often as every other day if you can fit in the time. I'd also recomend switching up your rep range. Sometimes I'll do 5 rep sets and work up to super heavy weights, and sometimes I'll work in the 12-20 rep range. If you really want them to grow, use both low and high reps.
One last thing is that you need to NOT neglect your hamstrings. All the muscles on the posterior chain work together, so working your hamstrings from both sides will actually help your calf development. I like to do SLDL's followed by leg curls then right into my calf work. I find when I do things in this order I end up hitting everything better, including calves.