The pyro. A maniac with a flamethrower, how else can it be put? Perhaps a man (yes, a man) in some fantasy world, the best ambush class of the game, or as he is commonly played, the annoyance right next to the "pro" annoyance scout.

For most pyros out there, they will argue with this section. For all you new players in the game, this is the part you can't skip.
The pyro uses the flame thrower to burn his enemies to a crisp for scout on a stick, or heavy bacon, or of course melted merc. The stock loadout is the flame thrower, my preferance of primary for pyro when I do play pyro, the shot gun is probably my suggestion for secondary, and for a true land defence, the homewrecker (Homewrecker is a sledge hammer that can remove the spies sappers from a friendly engineer's buildings, but does have a damage reduction).
On to step one.
The pyro is the kind of class you'll want to sit around a corner a vital spot on the map and ambush enemies as they run past, wether it be in a large group for a bonfire, or a single target for a simple roast. The best way to remain a good pyro and not go all W+M1 (Holding down W for forward and Mouse 1 to fire) to chase after them and constantly burn them, is to retreat, reason being the pyro's flame thrower range is very limited so you want to run away and fire with your shotgun the second they get out of range. The pyro also has an afterburn, the target will continue to burn after you light them.
Step two to be a better pyro and not some nawb maggot.
The airblast is a perfect tool for all pyros, wether it be the over-powered degreaser maggot, or the W+M1 Mother F**ker. The airblast can launch all projectiles except for bullets right back at the person who shot them, if your aim is spot on. Things such as, rockets, grenades, stickybombs, huntsman arrows, jarates, and the mad milk can all be shot back at the user for a nasty surprise. The airblast is also a great way to push a high value or target that is just too powerful off an edge or into a hazard.
Final Step.
Spy checking and advancement.
Spies can cloak and disquise as your teammates, don't be afraid to puff around some fire at your "teammates" and in areas where players call out "Spy!". A cloaked and disquised spy will catch fire.
Advancement is another thing every pyro needs to know how to do. The pyro works best around corners and from behind, or in little nooks where people wouldn't check to look. While advancing, keep in mind that if you're spotted, it's best to run backwards and fire with your secondary.

This is the section that most pyros will really fight me over.
W+M1 pyros are a common sight and can be annoying as all ****. They charge you while firing, sure this can be avoided with a counter attack from a knockback weapon, or a jump into water if it's near. Most of us will fall victim to the W+M1 noob, the one that will have a high score from simply being this annoyance, right next to the degreaser pyro.
The degreaser is a primary weapon that does less damage and has a shorter afterburn time, but has a 65% faster weapon switch. Sounds balanced right? Well the weapon itself could use a little more "nerfing" but is overall not the problem. The problem is when it is used to light, then airblast their target into a corner to get the critical hit with the flare gun against burning players, or the minicrits with the reserve shooter. The next big problem is the axtinguisher. It has been changed from crits to minicrits against burning players which is a great step for the better, but even minicrits after a shot with the flare gun or reserve shooter can make all the difference.
To all you new players, don't become one of these.

To all new players, don't become a W+M1 or a degreaser loser.

To all you players who are one of these...I just hope you see you're not making for a fair fight and you're just annoying as your brother, the scout.