Being fairly new to TF2 (about 100 hours play time) I am becoming steadily proficient in most classes, and am having a great time with them. However, one class, the scout, is eluding me. When I play as scout, I am killed very quickly and am lucky to get a single kill. However, when other people play as scout, they run circles around me and kill me quickly. Clearly they are doing something that I'm missing. How do I play well as a scout?
Scout is a class with a very high skill threshhold to clear - playing Scout and doing it well is very difficult, especially for a new player. They move faster than any other class, making it more difficult to aim properly. And they have the lowest possible base HP of any class (unmodified by loadouts).
Mobility is key to playing a Scout. You never want to be in one place for long. Jump, weave, and duck into side-corridors to get away from danger.
You are vulnerable, and you do not want to get into a head-on fight, even against weaker classes. Instead, use side-corridors to flank and get behind other players.
Your Scattergun (and the FaN if you have it) are powerful close-range weapons. Don't shoot until you're up close and certain of getting a full-body shot. The more pellets you can get into them in a single shot, the greater damage you'll do.
You can take down most classes in just two shots at close range, which is faster than most classes will be able to react. If they do, dodge, and if they are well aware of your presence, run. You are outgunned by almost every class that isn't support-based.
Avoid sentries. Always, always avoid sentries. Use Bonk! to get past them, pick them off with a pistol, slip by them if they aren't pointing directly at your pathway, but avoid them at all costs.
Finally, above all else, practice. Every class has a skill threshhold you need to get past before you're 'good' with them, and the Scout's the hardest class of all to get used to. Watch some video clips, watch what other players do, read the TF2 Wiki pages on Scout Strategy and match-ups, but practice above all else makes perfect.
The best way to get better with it is to train, and to know the pros and cons of the class, so look at guides like this one for example : http://www.wikihow.com/Play-As-a-Scout-in-Team-Fortress-2
The scout is faster, has double jump, but the price is a low health. Use your strengths and move as much as you can, so they can't touch you. All i can say is start with a guide for the basics, then train and watch videos of good players.
The top advantage of scout is double-jumping and speed. remember, because you have low health, never stop moving. if you want to kill players, jump around, run around them to make hard for them to kill YOU. Basically, be a nuisance.
If you play capture the flag(best for scout), there will be a point linking both team's bases, and that point will have many enemies. so go left right, jump around, to survive. you would want run past everyone(don't fight a group of people!) quickly, grab their team's intelligence, and return to your base afterwards. watch out for sentry guns.