One of the things that I love about pandemic is that it is almost entirely based on skilled movement. What you need to understand first is that its all about keeping and building momentum, meaning whenever you hit the ground, hold control to slide, then after a second or so, jump, and then repeat
(does not work going uphill). Another thing to do is gunjumping. Gunjumping is when you use your gun to accelerate your movement (this only works with objects close to you). This can be used to build up speed. This one only works with a pistol because they accelerate to top speed instantly. First off you need to find a flat surface, then slide jump, then jump again in the air, and turning around (so your back is pretty much facing the direction you want to go) and then shooting said flat surface, and then combine this with the previous method, and you have a way to outrun most zombies and cover hundreds of meters in maybe 1 or 2 minutes instead of the normal 5. These are only some tips and basics and you will learn more methods from experience

The other big key in pandemic is shooting. If there is a zombie coming at you in a straight line, stay calm and line up your gun. Depending on what gun you are using, you might want to scope in here (AKs & SMGs maybe not SMGs if theyre like right in front of you). Keep the crosshair trained on your target and keep on firing. If you run out of ammo (they dont die), use the movement tips from earlier to get a little distance (while reloading) and then keep up a continous stream of fire. If the zombie is skilled and they are strafing, it is best to use your gunjumping abilities to get some distance here, or if you have a pistol run, reload, then turn around and shoot them. Before they hit the ground, reload and shoot them while they are on the ground.

Conductors are strong zombies that spawn to break up the humans on the train. When a conductor is running up the back of the train, move closer to get a good shot, then back up while pouring everything you have into them. When you reach the end of the train, jump off and hope they dont follow you. If they do, gunjump back onto the train and repeat. Bombers can be easily dealed with by simply jumping onto another structure and then shooting them i.e. rooftops or cable car cables.

Catcher: Catchers are the most versatile of the zombies and have the highest melee damage. Get close and personal by strafing a little bit, as believe it or not this is enough to throw off most players aim. If you are swarming the train or cable car, you objective is throw the humans off, allowing them to be picked off by other zombies.

Mimic: Mimics are best used to infiltrate the humans by jumping on from above, or somewhere a human would come from, and once on the train or cable car, just start hitting as many things as possible.

Bomber: Bombers can die very quickly, and as such, you should hide behind cover and use smoke to cover your exact location and then quickly jump onto the train or cable car. Before anyone starts shooting you,it seems to be a little known fact that bombers can hit people, but just hit everything insight, which should provoke the humans to shoot you, and explode you withing close proximity of other humans.

Conductor: Not much here other than remember that your purpose is to scatter humans off the train or cable car, and that you are not affected by knock back, and that bullets are not very strong against you. However, you are not very versatile, and you cannot slide jump, limiting your speed to tat of a sprint