While trying to hook, click the ground in front of them. Instead of clicking on the enemy.. Also make sure there are no creeps or friendly guy in between you and the enemy.
The hooks can go through woods so hiding between trees will work wonder, when you can pull in unsuspecting enemies.. If you are finding hooking too tough, get shadow blade. Activate it and hook it 2 inch from them

As soon you hook do Dismemberment and activate rot. Also try to pull in enemies who have like 50% hp, it will assure you guaranteed kills..
I am no pro in Pudge, but these steps let me have easy hooks. Again, Pudge is a tough hero so take it easy on yourself
You can also Blink or use forcestaff to narrow the distance. having said that Shadow Blade and Blink Dagger/Force Staff will help you close the distance. But it kills the whole purpose of the hook. Hook is to pull enemies near you and not vice versa. So, I would suggest you practice hooking in Bot matches

Once you start getting good with hooks, people will start fearing you