The hardest muscles to make bigger by far are the calf muscles. People usually chalk it up to genetics and accept that if they don’t have big calves now, then they never will. I disagree with this. Plenty of people have made their calves bigger, and while genetics definitely do help, they are not the end all be all. You can have poor genetics and still grow huge calves; it just takes some hard work and patience.
The first thing you have to do to build calf muscles is realize that building calf muscles is the same as building any other muscle. The most basic principle behind building muscle is that you need to be in a caloric surplus. You have to be eating more than you are expending throughout the day. The most important thing to be eating a lot of is protein. Protein is what your muscles are made out of and without it you cannot build muscle. A lot of MOST OF your results with any type of muscle building program will depend on your diet. Your weight gaining diet should consist of ATLEAST 1.5 grams of protein for every pound of bodyweight but some people even go as high as 2. People get results with 1 gram per body weight but nowhere near as fast as if you were taking in 1.5 to 2. To make this process of eating protein easier you should buy a protein drink. Taste is the key here because you want something that you’re going to be able to drink every single day. I prefer Cytosport's Muscle Milk as it is the best tasting in my opinion.
After you get the diet down you want to work on your calf muscle training program. The key here is to pick good exercises and keep progressing in weight and reps with good form. As an example, the leg press is a good machine to do calf raises on because you can progress in weight every single time you use the exercise. If you can only do 100 pounds for 10 reps now, imagine what your calves are going to look like when you can do 250 for 15 reps. This is not only the key to building calf muscle, but also goes for any other muscle training.
A key thing with building calf muscles is that you want to train with highish reps. Right around 10-20 is a good range for calf exercises. Also you should do calf raises in a standing position as well as a sitting position because it works two different parts of the calves.
THE MOST IMPORTANT THING for calf muscle building is a tip that I cannot take credit for making myself. It came from a guy named Dante Trudel who is also responsible for a weight training program called “dogg crapp training”, which is a very good program, but only recommended for very experienced trainees. However, the calf training tip can be used by anyone interested in building calf muscles. It is honestly the best tip I have ever gotten in regards of calf training and it is what helped me build most of my calf muscle. Dante recommends that you do your calf training in this way: an explosive positive phase of the rep (when you push the weight up with the balls of your feet) and a very slow 5 second negative phase of the rep (when you let the weight down) with a 15 second pause at the bottom of the rep. Count or get a buddy to count to keep you honest. You should, and probably only can do this with one calf exercise. When you do this right your calves will burn more than you have ever felt. Keep up with it for a while, and eventually you will build some impressive looking calves.
For a more in depth view on muscle building from a no b.s prospective read How to Make Mucles Bigger.