There's no "best" place, because it depends on enemy movement and where your team is at (or going).
[Being on blue side, during lane phase]
If you put a Pink in your bottom tri-bush, it's a great vantage point and you'll probably deny some of the wards they try to put there, but if the enemy keeps going in there and destroying it then it's not a good spot for a visible Pink anymore. If their support keeps going in there to take out your wards, then instead I go place it behind the red camp (bush next to the ramp); that spot is good to deny counter-jungling and simply protects your tribush from further up the path.
http://i.snag.gy/16ePi.jpg
If the enemy jungler has a low cooldown wall jump, then putting a ward between dragon pit and the ramp will miss them if they jump straight over the wall into the bottom river bush, so you'll want to either A) ward the bush, or B) ward the dragon/ramp and over the wall by red tri-bush.
[Red side]
I like to put a Pink in the "banana" bush, which is the one near mid just above the single bush in middle of the river. This protects mid fairly well, and cuts off the river path to you while also helping against counter-jungling (you gotta put it far enough forward to see the ramp). If it can't be defended, you can place it further in (the bush to the right of the mid tier 1 turret) and it'll be of use for quite a while. You can also put it in your own tri-bush to defend from turret dive ganks from behind and a good spot to kill wards that get put over the wall (the spot I mentioned before to defend from ppl jumping over the wall).
http://i.snag.gy/M0ZfX.jpg
[Laning phase over, blue side]
If they keep showing up to your favorite pink spot to destroy it, simply cover a different area. Also gotta change what you're protecting later in the match. You can put them on top side too. If you're on the blue side, a good spot is protecting your mid laner from top just like red side does for them in the bottom half; the banana bush!
http://i.snag.gy/9mHdb.jpg
If your team is getting pushed in, a deeper pink in your own bottom side jungle may be good.
[Red side]
For protecting top side, the bush between Baron and red camp is a great spot. It usually lasts a very long time earlier in the game, and if you're contesting Baron you want it there to take out wards they place to defend from a steal. It protects the mid laner a little but, and again good for stopping counter-jungling. If they like to check that bush and still counter-jungle, you can put it further in to defend the Red buff and ganks to top after his Tier 1 tower is gone.
As for simple green wards, you mostly just want to cover the maximum area possible, which is in bushes and in view of both ramps and baron/dragon. Don't be afraid to place and replace lots of Sightstone wards, just recall to refresh them and keep putting them out as the team moves and objectives come up. Also put them in the enemy jungle to defend a split pusher (like if he's pushing red side bot tier 2 tower, you want one above blue camp at the intersection at least)
Don't forget: Face-checking brush is dangerous! If you have no idea where the enemy is, use your skillshots to check bushes. Always assume someone is trying to gank you as you ward. If it's really dangerous, like they practically own your jungle, don't forget the Twin Shadows option.