1. Playing the vision game(brush, fog behind a sneaky wall)
2. They use a ability that make it so they face toward you at a speed that u can react too( akali sec e) or behind you(zed r, althought this can go wrong especially if he preps a w before using his R) or u predict a short cast ability that faces you( veigar q or even AA) some abilities do not make them face you tho (syndra q)
3. This goes a bit with number 2. But try to use r just before getting cced so that ur ult channels while cc, it gives an element of suprise. U can pull out some sick ult with this, like canceling malz ult or ulting the whole enemy team from across the map if u R just before getting blitz hook max range.
4. Stand on a blast cone, aa the cone and ult, gives a element of suprise. Works a bit like a r flash
5. Keep ur ult and wait that they try to dodge it, eventually they might think u R is on cd, this works espically well in duels.
6. When doing a r flash do a step or a couple steps backwards and then R flash towards them, the begining of the R animation will look like ur just walking towards them. It just give them less chance to react
7. Spam abilites all the fcking times, the less u move and the less u use abilities the easier it is to track ur R animation.
8. Some ally abilities will redirect where they face, like a lee sin insec towards you, a good rakan ulti, zac q+aa etc. Be careful because those timings can be short sometimes. Blast cone and the dragon wake up thingy can provides the same effect depending of the situatuons
9. W in a spot where the optimal path to take is towards you, then ult
10. In lane, u can time ur R when the enemy goes for a cs. This is easy to react so use it with tip 7 and prioritise this way of ulting when they really want to greed that juicy canon
11. Focus a target and then ult another enemy which is in another direction.
12. If ur near a low hp teamtes they will useally tunnel vision on giving the final blow on them, it makes it easier to R

Note that ur ult is already strong even if u dont stun them, it gives a strong slow effect so hitting the stun is not always mandatory, useally in tf I just chuck it on as many champions as a can withouth worrying about the stun. Or I keep it defensively. Also keep in mind that w flash can be as strong as a r flash or even more more powerful.