If you google "what attracts mosquitos?" you will quickly see that there are an endless amount of theories and opinions out there for what attracts them, as well as ideas for keeping them away.
There were a few things, however, that most tended to agree on:
1) Body Heat. Some people have a higher body temperature than others. There is nothing you can do about that, those people will attract more mosquitos. But also know that if you are exercising or doing something active that is raising your body temperature, you are going to attract more mosquitos. (If you've been looking for a reason to skip a workout, you're welcome)
2) Beer. It is very sad and unfortunate, but it seems to be true. Beer drinkers attract more mosquitos. The reasons as to why can vary, some say its the smell of beer on your breath, others say its the smell of the alcohol in your sweat. The one that makes the most sense to me is that alcohol raises your body temp, which takes us back to #1. So stop drinking beer....which is very unlikely so you're just going to have to deal with mosquitos.
3) Dark Colored Clothing. Mosquitos can't see very well, they only see silhouettes and outlines. Dark clothing gives them a better silhouette to work with, while lighter colored clothing blends with the background and makes it harder for them find you.
4) Carbon Dioxide. This is the one that attracts mosquitos the most, they can detect carbon dioxide from up to 150 feet away! Everyone exhales carbon dioxide, so there is not much we can do about this one. Some people do exhale more carbon dioxide than other, which means they are going to be more of a target for mosquitos.