Sentries

The spawn of the engineer, can take a scout down every time. Well almost. They are normally placed in some dark corner so you probably won't spot it the first time around... unless you have the scanner running.
Sentries can be taken out easily using a combination of the nailgun and the scouts speed/strafing abilities around corners. A level 3 sentry will start shooting rockets at you as soon as you enter its field of vision (fov) so be careful of splash damage they may cause. Remember to stay as far away as possible when trying to attack them.
Also, if you can get below a sentry somehow (They can't shoot down afterall!) and can see it's muzzle, then you should have no problem taking it out.

If do you come across a sentry positioned so that you can't hit it much whenever you have sight of it, then try a concussion grenade in its area. This seems to slow down the reaction of a sentry, but it recovers quickly (So get the flag and run!). You may also be lucky enough to concussion the sentry's engineer if they are guarding it. I'm not sure whether the TF code says sentries can be concussed, but it seems to work for me everytime.
 

Grenade Jumping

Down to the nitty-gritty. Everyone knows about rocket jumping, and it is possible to perform grenade jumping. With the scout this is done best with concussion grenades, and timing is critical.

There are several methods you can use, depending on whether your on land or under water. On land, just throw it, stand on it and jump just before it goes off. This is harder to describe and best explained using a demo.

On water, there are 2 methods depending on how deep the water is. In general, swim up and float on the top of the water and start priming the grenade. Look down, and just before the grenade is about to explode, release it. You should end up going straight up!
All you have to do then is to adjust the angle that you look down in the water depending on the angle that you wish to jump back.

Secondly, in shallow water, lay a grenade on the floor and swim to the surface directly above it. When it explodes you should be propelled straight up again! Simply adjust your position on the surface of the water to adjust the angle that you will fly up at.

Both of these techniques can be used to jump from the water to the snipers nest on 2fort5 and bases, and to the flag room on well6.

Another technique is the double-concussion. Lay one grenade on the floor and as soon as thats dropped prime another. Jump as you would the first technique, keep hold of the second grenade and you will get extra height when that goes off. Especially useful on the lift in 2forts, but requires extra practice.

You can also use the concussion grenade to propel yourself across large areas quickly. For example, try laying a gren in one of the entrances on 2fort5, stand in front and jump before it goes off. If you don't end up on the other side of the map then something went wrong!

You can concussion jump on just about any map. Just be creative and think about ledges etc you may be able to reach, and where water is placed in the map. Look out for positions other people are jumping from. Not only scouts but medics also carry the concussion grenade.

Capturing

The reason for the scout. The reason for TF. If you want to be a scout, you need to be able to cap, and cap frequently. Seeing as 2forts appears to be the basis of every other map, lets examine a cap on it:

1. The bridge.
Snipers will be pestering you a.s.a.p. One way to deal with them is to shoot. Another is to swim for it (Or grenade jump from the water). However I prefer to dodge them. Strafe, strafe, and strafe. Once your half way across the bridge the snipers job is 3 times as easy, and they will ALWAYS try and hit you at the point just before the end of the bridge. Also if the sniper is an lpb then getting past is even harder.
So, when you think the snipers is about to shoot, or if you see the red dot suddenly, don't lift off your forward key, just strafe backwards. The sniper will shoot, leaving you to stop strafing and you'll run straight past.
This strafing backwards technique is very useful if practised, as the opposition is put off by both your sudden decrease in speed (Don't actually stop still, else your a sitting duck...) and the fact that they missed you!

Another one is that you can actually jump off the bridge, over the sides and off, if you time it right just before the big blocks at the end of the bridge, cutting the corner.

Oh, and when on the other side, don't always go heading straight in to the depths of the other base, throw a concussion grenade for the snipers and give 'em a finger!
 
2. Ramp room.
Next up will be the ramp, which should be renamed the sentry hall, or something... If theres a sentry, shoot it, concussion it, dodge it, everything and anything. Always worth throwing a conc grenade to the top ramp as 9 times outta 10 there'll be a soldier or HW Guy nearby.

You can also concussion jump from the ramp room floor to the ramp leading to the lift.

3. Flag entrance route:

Choice of 2 main routes. If it's free, go down the lift. You can actually get down the lift shaft without loosing any health, by running in to one of the two corners of the shaft near the lift. Needs practice first time round but is easy once mastered. This also lets you get down silently, and it's usually the pain noise that alerts the defence to your presence.

If the lift isn't to your taste, then try the spiral just round the corner. Only problem with this is that it's near to 2 enemy respawn points, and is often defended by a demoman or sentry or both.
Drop caltrops by the first respawn exit, and concussion the demoman who may have the spiral piped. If your lucky you may come across a team member, such as a rocket jumping soldier, somewhere in this area. Always let him go first and use his heavy artillery to take out or damage some of the defence. Once dead, nip in afterwards, concussion any remaining defenders and sentries, and get the flag.
 

4. The escape:

So you've found your way to the flag room, and there was no one there. Right? Well either it's a bad defending team, or they're all waiting for you on the way out. If you had to fight past loads to get here, good luck on the way out. Having said that, as long as there was no sentries in or around the flag room, you should be able to get past 5, maybe 6 other players, depending on your health state.

If you've had the practice and have the grenades, try and jump up the lift shaft using 2 concussion grenades. Very tricky but worth a try. If not to your taste, the only other exit is the spiral. Remember there are 3 corners here, and just before the 3rd, stop. Often, demomen etc. like to drop grenades down here when they see your glow come up. When any which may have exploded have exploded, go.
The best place to exit the fort is quickly out of the grate area, just make sure there's no one waiting for you, blocking your way. If there is, go left and out the ramp room. The next decision is water or land? Land if there's less than 8-10 players on each side, as it is unlikely you will meet anyone from the other team on the way, plus, you or a teammate can regain the flag quicker when it's on land. If you do decide to go by water, it's one of the safest routes, but should something happen and you can't find the flag in the water, don't blame me.
Once in to your home base, hit it up to the snipers ledge and capture that flag. 10 frags thank you very much. Tip: Bind a key to some annoying saying you use alot and once captured, press that darn key until your keyboard burns up!
Next step: Get some R&R (Reload and Recap!).
 

Defence

Believe it or not, you can use the scout as a defensive player, with several different styles of play. The scouts ability to unmask enemy spies can be useful around flag rooms, just brushing past any "friendly" players entering the area. Of course, should an oppossing scout manage to get away with your flag, the only class capable of keeping up with him and stopping him is a scout. When stopped, caltrops can be used in the vicinity to slow down any other enemies attempting to take it, while your main defense catches up to help guard it.