Yesterday I was at a festival with some friends and I fainted. I didn't actually loose conscious but I wasn't hearing very well, I couldn't see well, and I had all those symptoms that you get before you actually fall down. I sat down before it happened and after being very nauseous and eating sugar, I felt OK. A bit weak, but OK.
This is not the first time this has happened to me. Yesterday was a very hot day, I hadn't slept very well, and had two beers at the festival. The other times I had this feeling were when I hadn't eaten for long, or when I was under the sun for too long, too many people around, etc.

This doesn't happen often but it's pretty scary when it does.My question is: Should I look into this or am I just one of those people who faint easily? When should one seek medical attention?

Other than being checked for diabetes, you could spend a little more effort on hydration before thinking of all the other medical conditions it could be, which are many. Most all fainting or semi-fainting in hot weather is a result of dehydration. Alcohol is just going to make it worse, especially if no food with it and no other liquids on a hot day. Carry a water bottle with you and if you don't like plain water, some lightly flavored selzer or plain water. Stay away from beer and Coke. Sport drinks aren't too bad. The amount of sugar you need when your blood pressure drops is tiny, 2 ounces of OJ maybe. Too much sugar isn't good.