Saw a few of these, figured I'd give it a shot.
(Disclaimer: I am in no way claiming I'm a particularly good Scout. These are just the things I like to keep in mind while playing.)
1. Just because it's new, doesn't mean it's better. The Vanilla Scattergun is increadibly powerful and reliable in every situation. FaN is a mobility tool, Soda Popper is good for picks and ambushes, and the Shortstop gives mid-range capabilities, and all but the Scattergun suffer in sustained combat.
2. Know your secondary. The Pistol is useful as hell, but know when the unlocks are useful in what situation.
3. Melee is useless. Your primary does more damage faster in the same range. Get an Atomizer.
4. Flank. Try to never take on enemies head on. Come in from the side or from behind.
5. Know health and ammo drops. Even a little damage is bad with such a low hitpoint class. Know where to heal up on every map you're on.
6. Know your map. Scout is basically a free kill to most classes on linear maps like Payload and Attack/Defend. Play open maps with a lot of routs to flank from and very few choke points, like 5CP and, my favorite for the class, KOTH.
7. This to me is the most important: MAKE KEY PICKS. Always kill Medics first. It is always worth dying to get rid of one. Other key targets are Demomen, other Scouts and Snipers. Kill them, then go for everyone else.
8. Just because you retreat, doesn't mean you lost. You have low hit points, if you think you're going to die, get out of there and heal up. You're playing the fastest class in the game and can kill almost everyone with 2 hits. You can come back.
That's my advice. Any thoughts?