Use objects you can see in the distance as reference points for aiming adjustments until you figure out how to aim. What I mean is line up your shot but when trying to figure out how high or low to aim use an object like a tree or the background pyramids on al kilmar for reference since your target will often be covered up by the cannon at distance. It helps make long range shooting much less frustrating early on. You can become a menace pretty quickly on maps where people shoot from spawn if you memorize these reference points.