Leveling Up

I would like to know is there any other ways besides attacking people and leaving them and been active to level up.

ways other than being active? well, no. general activity is how you level up period. everything you do provides experience. if you want to level up quickly, your best choices are combat based (attacking and leaving, and buying defends from lots of different people). otherwise, your best chance at leveling up quickly is just to play constantly.

Doing crimes, train in gym,

Be active enough to use all your nerve and energy generated throughout the day. If you're active enough maybe take xanax once a day for more e but I don't suggest more than that till you hit 15 and if you OD leave your revives on and hope someone helps you out if you can't afford to pay for one right away. And try not to power level much after 15. At that point stats should start becoming priority more than leveling unless you don't mind being a punchbag.

Main thing though is be active...

everything you do on torn gains you some experience to level up.. but it takes forever to level up naturally.

if you want to gain levels quickly attack + leave is by far the best option.

Get in a nightclub job
Go inactive for a few years.
Come back and use all your job points in experience.
Level up without being active.
Profit??

Get in a nightclub
Go inactive for a few years, waiting forever for your master plan to finally come true
Return to find you were kicked after 3 days of inactivity
Profit?