The shirt you wear can make the difference between a fun day out on the green, and an uncomfortable afternoon of sweating and itching. When looking for a golf shirt, do not make the mistake of buying based on looks alone, or just buying "for the brand." Look for the following four qualities, which are essential for a comfortable, functional golf shirt.
Just because golf shirts made from cotton still exist does not mean that one should have a place in your closet. Cotton will absorb moisture, making you uncomfortable should you sweat on a hot day. A shirt made from a breathable, artificial material will wick moisture away from your skin, preventing you from overheating. It is also less likely to shrink in the wash, so you won't look shoved into it after a few washes.
A wide-enough neckline.
Because golf shirts are collared, they can be pretty itchy and uncomfortable against your neck if you buy one with too narrow a neckline for your physique. You'll have to try a shirt on to determine whether its neckline is right for you. Different brands tend to offer different widths, so if you're struggling to find a shirt with a neckline that does not pinch or rub, you may have to switch brands.
Most of the better brands sell their shirts with an extra button or two. Check for this because it can be a real life saver if you lose a button in the wash or when taking the shirt off. Without a spare button, you may have to get rid of the shirt, since it can be hard to find a button to match identically. Sometimes, the extra buttons are sewn into the inside of the sleeve. Other times, they are attached to the tag in a little baggie.
To look proper on the green, you should tuck your golf shirt in. If it is too short to do this properly, it may keep coming untucked, which will get annoying throughout the day. Tuck the shirt in when you're trying it on, and make sure it stays tucked when you raise your arms above your head and take a few "pretend" swings. If you are broad in the abdominal area, you may have to look for shirts sized as "long" to ensure they stay tucked.
If you find golf apparel with the qualities listed above, you're on the right track towards comfort. Then, you can focus on the more enjoyable decisions -- like what color or pattern you want.