Calves can be very tough to develop, no doubt. Try doing this for calves if you've been working out for awhile, I found it on another website: using one step of the stairs or a cinder block or whatever, do calf raises with one leg at a time using your bodyweight. Do as many as you can for each leg. Concentrate on keeping your form strict. Repeat with the other leg. Don't do more than a couple of sets your first time doing this. Use your hands to balance yourself against the corner or wall or whatever. When this exercise fails to create a muscle pump in your calves you can hold a dumbell in one hand while doing them. It's an old recipe, but one that I really like. If you can find a workout partner, you might try doing resisted toe-ups to work the tibialis anterior muscle, which is located on the front of your shin.
I think that forearms are extremely difficult to build up personally. Just like calves, what you've been given genetically is a big factor. Persistence will pay off if you approach training them in the manner that best fits you. Positive visualization helps a great deal as well. If you're really serious about building them up it would be worth it to pay a good personal trainer for a session to glean some insight on training tips. Remember that everyone is different and that you might need to personalize your workouts to your particular body type, metabolism, etc.
I never had a problem with triceps however, and I don't really hear that much about it being a problem area...biceps seem to be harder than triceps if the genetics aren't there naturally, but that does not really mean anything specifically. Keep in mind that arm size is probably 60-70% tricep size (if not more) and that biceps are also worked during back exercises.
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