Here in my personal opinion Puj's hook and Mirana's arrows both are similar, both require anticipation and judgement plus most important some common sense.
I found it easy to hook after I had some control over Mirana's arrows, but thats a personal thing. If you straight away want to go into hooking
Check it: Always first check your hook range, by using it in base or some random hook at hero, this way you would have sense of how much distance you can cover and the animation time as said above. Also make sure of mana, many times it happens with me I hook but there is no mana left for dismember, it causes epic fails.
Totally Blind: If you are going for blind hook, hook in or near most probable regions where hero's have been spotted frequently in game or where you think the can be. eg naix or some other farmer at nc's.
Escaping Hero: For escaping hero notice the trajectory before he disappears, keep in min his movement speed and yours, whether he can blink or not plus the distance your hook can travel.
Sometimes people try to hook only when they can rot and get a kill, but you should also hook whenever you can especially if you are full mana, not only you are 100% sure to get a kill. In this way you are using your mana efficiently.
Try to save people with hooks when they have plenty of mana and there is minimum risk.
I am not a expert but these are the points I think can help a new guy.
The more you hook the more you get better as simple as that. You may screw up games, people will shout at you but it's worth training to get better.