Fede123

I know what a linear 3-bet range is and when I should use it, but what isn't clear to me is how to construct it.
Example: LJ opens (he opens 15%), I'm in the HJ and I decide that I want to 3-bet linear because I don't want to have a calling range...
Which hands should I 3-bet and why?
How do I know if I'm 3-betting too nitty or too loose?

(Sorry for my English)