The Resource Constraint
In your average game, each player can only place 4 wards maximum at any given time, 3 stealth wards and 1 pink ward. Any more than that, and they get wiped off the map starting from the earliest one placed.
Assuming your team doesn't help ward (which they usually don't), that means as a support you'll need to be hyperefficient in ward placement. Don't worry, The Art of Warding Baron is here to help!
The "Basic" Baron Ward
This is the classic "baron ward". If your team asks you to ward baron and you do this, they're satisfied and at most Elos you'll get a little pat on the back for being a great little support for doing what you're told.
However, what's generally going to happen is that the enemy support (also doing what they're told) is going to use his red trinket as pictured above, take out your little ward, and your team may either lose baron, or get baited and die.
Not only that, but if you've lost a significant number of turrets, you probably don't have the map control to even see the the enemy team in time before baron goes *poof* and the game ends with complaints of people being out of position even though baron is "warded".
However, what's generally going to happen is that the enemy support (also doing what they're told) is going to use his red trinket as pictured above, take out your little ward, and your team may either lose baron, or get baited and die.
Not only that, but if you've lost a significant number of turrets, you probably don't have the map control to even see the the enemy team in time before baron goes *poof* and the game ends with complaints of people being out of position even though baron is "warded".
So what's a support to do?
Spot #1: Overall Map Control
This spot pictured above is actually somewhere that I thought everyone warded, but time and time again has proven that oddly enough, this spot seems to be obscure and unknown...the middle of the map.
There's a reason why the mid turret is so important, and that mostly revolves around map control and more importantly, SIGHT.
Once you lose your mid turret, you lose a significant amount of sight from the enemy as they roam around the map through the jungles and other lanes. The simplest solution to this problem is placing a ward there, but for some reason most people neglect it completely. As pictured here, this ward is actually completely out of range of the turret, even if it was still up.
This is the single most important ward you can put for all objective control as it gives the most vision over the whole map.
Generally, people consider themselves invisible if they're behind their line of creeps. Once they take down a mid turret and their creeps walk past that river, almost everyone feels safe enough to just walk straight through mid to wherever their destination is, since that's the fastest way from objective to objective.
If you manage to take a deeper turret, place one up there as well, as it will give you more sight as enemy champions leave their base. The further up you manage to control, the stronger your team can be offensively.
Spot #2 - VS Blue Side Ultimate Ward Placement - The Holy Trinity - Offensive + Defensive
Going back to Baron however, if you're playing purple side VS blue side, these three ward positions will give you the most vision over anybody trying to get to Baron. This, combined with some variation of Spot #1 will ultimately give you absolute confidence that if anybody goes in any reasonable path with ideas about Baroning, you'll know.
After placing these down defensively, it's a good idea to go back to base and recharge your sightstone just in case they start clearing your wards to prepare for Baron.
Spot #3 - VS Purple Side, Ultimate Ward Placement - The Holy Trinity #2 - Offensive, add Anti-sweeping #2 for defensive
Conversely, this is the ultimate placement once you're actually doing Baron if you're on Blue side vs Purple side. If you're not actually doing Baron, then it's better to place the pink in the same position as Spot #2 and also use Spot #4 as picture below. In the image above, one is behind the mini-map. (A bit of a fail on my part)
The Baron ward on the top left of the map can be done from inside the pit. For more information on how to do that check out the warding over ledges guide, it's the second picture down.
Spot #4 & 5 - Entrance to Purple Jungle
These two are the spots where purple Team dies the most to blue team camps. They're also the spots that cover the route that a purple team will always take when they realize Baron's in trouble and they need to defend it.
If you're on purple team, be very careful when entering these spots with no sight on Baron, and for blue team, these are great warding spots.
Sweeping/Pink Locations
Pink Location #1
Pink locations are pretty standard, besides placing one right smack in front of Baron, this one is is the second most popular one and can often stay unnoticed for pretty much the whole game sometimes if you place one early enough. Generally in higher Elo games the mid laner or jungle will plop one up there and it'll stay there for the next 20 to 30 minutes.
As you can see the range is pretty big from that spot, and can reach both the pit and a little part of the ramp. You'll mostly use it to clear any wards actually in the bush and anything outside the baron pit though.
Ideal Sweeper Spot
Unless you know exactly where the enemy has placed their baron ward, this is pretty much the standard spot you want to sweep if you haven't upgraded to Oracle yet (which you should do because it's amazing). This sweep covers both bushes and is pretty much a guaranteed find if you saw a support come from this direction. I'd recommend warding that bush right underneath though, or you might get picked off.
Anti-Sweeping Locations
Location #1
I like this spot the best for preventing sweeps since it's just out of range of the bush pink and gives you a good amount of sight on baron pit (perfect for picking off those ranged squishies).
You could probably also do with a bit higher, but the point being if they sweep Baron pit and near the little bush, they won't find this ward.
Location #2
This spot is also pretty popular as well, and illustrates why you should either bring two pinks to Baron, or upgrade to an oracle. This spot is especially popular on purple team when trying to keep sight of the Baron pit.
Conclusions
Hopefully this gave you some ideas for your next battle for Baron control. Just remember if you're not playing support, not everyone has read this same guide so they might not know better (Point them to this page). They're just trying to be a good little support!
Meanwhile, share your thoughts and comments below! Do you have more recommended spots? Think I'm missing some super awesome secret spots? Comment!
Thanks for reading!