The scout’s strongest attribute is his speed and agility. ALWAYS stay on the run, and when fighting an enemy double jump in random directions as often as possible. The longer you keep firing without being hit, the more discouraged the enemy becomes, and even if you don’t kill him, you can force him to retreat, thinking he is being beaten.
The pistol is a very good choice for medium to long range harassment, especially since your primary weapon is next to useless. When you think about it, only the sniper rifle and handguns are any good for instant long range damage; the minigun is inaccurate and rockets and grenades are slow. With the pistol it is easy to dish out damage while taking none yourself, and is often underused. Great for picking up cheap kill assists.
The scatter gun is pretty ordinary at medium range, but lethal at point blank. If your enemy hasn’t seen you or doesn’t appear very competent, try and get as close as possible (make liberal use of double jump) and gun him down. If you empty your clip, it may be easier to switch to the baseball bat to finish him off. When using the bat, run circles around your target, occasionally changing direction to circle the other way. Once people start getting batted, they get very confused and disorientated and pretty much focus on running instead of fighting.
Given the scattergun’s short range strength, scouts can be devastating if they are able to attack the enemy troops from behind. Always be looking for ways to sneak behind groups of enemies, such as the water in Well or various routes in Granary. If you can gun down a few enemies without being seen, go into hiding behind enemy lines and jump out when another opportunity arises.
The scout’s double ability lets him jump twice as high and more than twice as far as the other classes. This often allows him shortcuts to high places and the ability to jump between platforms with ease. Use this to your advantage and maintain the high ground against your opponents when possible. Wait for an opening (especially if they haven’t seen you) then jump down and feed them some scattergun.
Don’t be afraid to run away. If capturing a control point, for example, you are set upon by superior numbers, simply retreat (they have no chance of keeping up), lick your wounds with some health kits or medics, and jump back into the action from a different angle. Better than dying and having to wait 20 seconds to respawn.
A sentry gun isn’t the end of the world. Crouching and peeking slowly out from a corner until you can see a corner of the sentry but it can’t see you lets you attack the sentry at just about any range (the pistol is surprisingly effective). This trick only works if you are alone - if there are any enemies around they’ll most likely harass you, not giving you time to get your shots off, and if an engineer is repairing your pistol will be pretty much ineffective.
Basic, level 1 sentry guns are even easier to deal with. The scout can circle strafe faster than the sentry gun can rotate, so you can simply run circles around it while smashing it with the scattergun.