Q =
1. trying to shoot with literally the tip because xerath an astonishing range and enemies will not believe that they can reach
2. Q is not like in the shot right away so you can try to get the happiness of objects, such as a dragon or baron. (Of course if you have a ward there and attacks him opposing team)
3. Once you have a full build or simply massive damage, you can easily fix the entire line minions so that after 30 minutes (for example) "last hits" a piece of cake

W =
1. when you hit your opponent in the middle of a very slow (if you do not go too well but you hit the enemy spowolnisz but not so much) so you can easily hit the enemy with Q. This way you can easily and reliably harass the enemy
2. gives a vision so you can easily check if the bushes there is no enemy
3. Can you escape getting exactly the enemy

E =
1. of course, to stop the enemy to escape easily
2. Also on the line would then do a combination ewq and ult when you have to strike it right away (if it is sufficiently low on health)
3. vision as well as how you are going and when you go to shoot the E immediately stop the enemy if he was sitting in the bushes, but I would have recommended the use of more like a vision of W as it can sit in the bushes, for example, 2 enemies and then stop only 1

R =
1. First and foremost, it is designed to do completion ult from a great distance enemies
2. important in teamfight namely attacking ruler or simply a person who would easily kill your entire player
3. I have the "tactics" that when I see an opponent who is on our ward turning it on and wait for 3,4,5 ult sec and of course when you are low on health or have a lot of damage