League of Legends (LoL) Question: How to train skillshots?

Consider the enemy.

• If they're not moving to dodge your skill-shot, probably don't overthink to predict their movement. This is especially applicable in lower elos where players aren't consciously dodging.
• Think about what the enemy wants to do. For example, if someone is last-hitting, their attention is on the minion and not you. Likewise if someone is walking back after a trade, they're focused on their cursor moving back and not you.
• Think about their options. If they can walk in many directions it's useless to think about, but if their options are restricted such as wedged in between a turret or they're being flanked by an enemy close off their paths for escape.
• If there is forms of crowd control, such as slows or roots, be patient and wait for the enemy to be movement inpaired. This includes animation casts, such as Caitlyn channeling her piltover peacemaker.

Consider yourself.

• Quick Cast is good for landing skillshots. Your abilities will process sooner and leave a shorter window of time for your enemy to act.
• If it can be helped don't be predictable. If you're walking up, you're thinking to trade. The enemy will look for moments where you're looking to land skillshots and perhaps make an attempt to dodge. Pretend you're doing something else such as moving to ward or walking up for creeps.
• Incorporate your flash. This is situational but this can leave less time to react. For example, Ahri can cast her charm then flash to extend the distance. If your champion can't do this, it may still catch the enemy off guard.
• Force a high tention moment. This is when you can walk up and the enemy can't do anything due to your advantage. If they're being overly zealous with their movement to dodge, just walk up and they'll bridge the distance for you to land skillshots.

Also try not to overshoot because often times it doesn't work out. Even if you predict a huge step in a direction, or a flash, it's very difficult to know the trajectory the enemy is going.

Aim for the feet.
Because of the game's perspective, everyone's hitboxes are typically located near their shadow. If you want to land your skillshots more often, aim for the feet.
Here's an entire article I found that helps explain it more.

I can't add to BIG DADDY WILL too much so i just suggest to watch this video from 9:55 about how to use you skill shoot as prediction to what the enemy will do
https://www.youtube.com/watch?v=ChtdLNhi684