What are ways to train ones lasthitting skills

I highly recommend you sticking to one role and becoming an expert in it instead of mastering different roles. But for the sake of the question;

10 min farming training:

• CS farming sessions should be 10 minutes. (Actually 8 is the perfect number, but for calculation ease we used 10)
• You should not have any runes or masteries when you are practicing last hitting and you should not power up skills. This will greatly help your early game last hitting with non-ad champions and improve your lane freezing skills.
• You need to train everyday before playing and train with each champion you play.
• Find a buddy who will also follow this training

After you guys really master this training with every champion, you are ready to do the same training with an added element: Harassing

• 2 champions in one lane you have to last hit like before .
• When your opponent gets a cs, you can hit them only once, 0-1 second after they get a minion kill.

This will improve your harassing ability, you will feel more comfortable about when you have to harass and when you will get harassed after you master this training.

Mastering this training guarantees Diamond1 in any lane except jungle and support.