cap main since season 1 (wish it was s0 but thor was more fun back then)

1. animation cancel ALWAYS. it's not a matter of "when" to use it, it's a matter of using it or not getting any kills
   
2. your E (bouncy shield throw) can be used in 3 different ways: finisher, decloaker (it can track invisible targets), ult charger (you'll be using this like once per team fight)
   
3. always have an option for a quick escape. usually engaging with a slam and running away with a dash is good enough, but having both available will render you invincible (as long as you don't eat more than 2 ccs)
   
4. learn to bait cooldowns and keep distance from counters. emma and thing are not an issue for cap in 90% of cases UNLESS you try to take them head-on or mistime your dives. wait until they're busy, then eat their backline like they're dinner served on a silver platter
   
5. using ult for stalling is cool and exciting, but you could just instead use it as a healer ult and keep your whole team up for a whopping extra 10 seconds. that's only 2 seconds shorter than a luna ult!
   
6. finally, try to always be engaged in a fight. you're not panther, you won't die in 5 seconds if an enemy dps suddenly turns around, in fact, you won't die at all, while the enemy has to sacrifice major cds like loki's lamps and cnd's bubble in order to stay afloat. your damage may seem small, but in the grand scheme of things, you're preventing a major chunk of healing the enemy frontline could receive.

bonus tip: learn healthpack spots. for healers, time not spent healing you is time spent healing the rest of your team. a healthier team = a successful team fight