Want the tight t-shirt look then you need to work on your triceps.
Firstly if you are looking at this article then you should give yourself a pat on the back because it means you are smart. If you want bigger triceps then you most likely wand bigger arms and you know that the way to achieve bigger arms is through developing the triceps not as most people wrongly the think the bicep. The tricep is the much larger muscle, for a start it is called the triceps – 3 as opposed to the biceps – 2. Now even though there are 3 muscles that comprise the tricep and they can all be worked individually in different ways there are really two main exercises and one common mistake that everyone makes. Stop doing extensions, they are very limited and will just give you definition, you have to remember the triceps are relatively large strong muscles so to make them grow they need to be treated as such. That means for size you need to do dips, body weight until you are strong enough ot wear a weight belt and close grip bench press. Don’t worry if you work other muscles such as the chest and shoulders as secondary muscles. I need to emphasise the point that you need to do different exercises working different angles such as the two discussed as different parts of the tricep extend the arm in different directions. And don’t overdo it 3 or 4 exercises with 3 sets each is plenty, it can be worked out in conjunction with biceps or another muscle.
Oh yeah and eat to grow!