Where to ward

for good wards you must know the enemy's gank possibilities, it's not the same an evelyn lvl 2 gank to one with jarvan/shaco lvl 2, even a zac, in short I recommend you to analyze the enemy composition and see how possible is a gank or a botlane roaming, some champs are more of powerfarm, if you are in group with the jg you can abuse a fiidlesticks, evelyn pre lvl6 as long as you have line pressure and do good tracking to the enemy jungler.