start with know how to ward and watch your wards. watch your teamates. go to your jg camps or lane. do your thing
you can gank at lvl 2 using your fear (e)
best at lvl 6 so you can jump in on mfkers
wait in brushes to trap your enemies.
and wards.

dont feed. dont go in all by yourself unless youve gotten your w down and can judge effectively.
let your passive take out the first camp (reds either side first) then jump to blue and use your first smite on the blue camp
then just play
either be a **** and selfish and one sided or be a badass jg and get your lanes right. even if your 1/8/11

your goal as a jg is to get your team fed. if you get fed then sweet.
keep in mind its about the xp and gold.
sometimes just back away and not fight. dont get tempted and dont get greedy.

wait. and gank.