Here's some advice I posted on reddit
Mess up soldiers by changing your distance from them. Its really easy for soldiers to aim their rockets from left to right, but hitting the ground at the right distance is whats tricky.
One thing you can do to dodge projectiles is to strafe back and forth in one place and wait for them to shoot at you. That's when you move out of the way. oh but Mr. advice guy! why would I ever stay in one spot? Well if you're standing still,you should know where they're gonna shoot, which makes it easy to get out of the way. This tactic is terrible for close range encounters, but if you're fighting at mid to long range it can be really effective.
This is the most important tip for dodging. try to actually, you know, dodge the projectile. Don't just let it fly on towards you and hope it doesnt hit you. Make a conscious effort to get out of its way. Even if you dont escape the splash you will still take less damage. Lots of players think they're dodging when all they're really doing is spamming WASD and destroying their spacebar.
When Jumping you should almost always airstrafe. This makes it harder for anybody to hit you with a direct from a projectile and its also a bit harder to hit with a hitscan weapon. If you don't know how to airstrafe watch this tutorial: http://www.youtube.com/watch?v=kvYRamyNxv0
Pay attention to what weapon the soldier/demo you're fighting is using and change your style of movement to make it hard for them to hit you with that weapon.
If you're really desperate, do 360's in the air. Sounds gimmicky I know but it does work lolololololol. If you spin around really fast your characters model can get a little funky. Sometimes while im reloading ill spin around and look backwards to throw the enemy off. If you're going to do this you need to be very comfortable with your aim.
Against scouts and people shootin' their shotguns, you wanna stay on the ground and spam WASD really fast with the rhythm of your terrible 12 year old drummer neighbor. Don't just spam just A and D. You need to throw in some W and S too. Screw with their depth perception yo.
Do something WEIRDDD. jump just once, stand still for a millisecond, jump on top of the light switch on the wall and do a 360 taunt slide >___> .... I think you get the idea.
When you're trying to jump onto a prop to avoid splash damage try to it in the least predictable way. If the soldier knows you're going to jump on to the crate on badlands mid it isn't too hard for him to hit you with a direct. You can also try faking going on to props because most soldiers will expect you to jump on to it.