There are two different muscles in your calves, the soleus and the gastro-something. One (gastro) is worked best with standing raises, and the soleus responds more to seated or donkey raises. Most people's calves are not symmetrical, from sports, and other daily activities. Spend some time working your legs individually to make sure they're fairly even. Calves love lots of weight and lots of reps. There aren't many variations to the calve raise so just split your time between the standing and seated raises, pile as much weight on as you can, and push out 15+ reps. Take them slow, so you avoid achilles problems, and hold for a count at the top, squeezing the muscle.