The simplest way for you to make a difference is to compare with english this and that. The problem is because there is also onakav, onakva, onakvo, you also translate with that. But the basic rule is:
Ovakav=next to the speaker
Takav=next to the listener
Onakav=far away from both speaker and listener, next to the third party
Hoću ovakvu jaknu-I want the jacket like this (next to me).
Hoću takvu jaknu-I want the jacket like that (next to you)
Hoću onakvu jaknu-I want the jacket like that (next to him)
The same is with ovako, tako, onako, but these are adverbs