I wonder with or against which team composition you would pick Bard. What are his strengths and weaknesses? How should you use the tools available to him? For me he is still a bit of a mystery so I would love to hear some opinions on him.
For me, I see Bard as an amplifier to your team's power. If your team is strong, he will make them stronger. If your team is weak, Bard can make plays, but he can only do so much for your team.
They need to know how to act upon your skill usage. Meaning, they need to know when to use your shrines, follow your portals, respond to your ultimate usage, etc.
Bard is there to set up plays and basically make life easier for your teammates by ulting escaping enemies, taking enemies out of teamfights, saving enemies, slowing them with meeps so your allies can catch up, flying through walls to cut off enemies, save allies from doom with your ult, stopping dragons/barons, letting you towerdive by ulting the tower. I mean, what Bard can do, the options are literally endless. I was primarily a top lane main before the release of Bard. I mained Garen top and when I had to support, I usually played Braum or Taric. Honestly, because of Bard's potential of what he can do in this game, I'm slowly considering becoming a support main.
Here's the thing about Bard though, you're going to screw up. I 
-tee it. You will screw up eventually. Whether you portal your allies into imminent doom, ult your allies instead of your enemies and end up getting them killed or even something I've done recently being of mis-timing, ulting your enemies when Ziggs is throwing down his ultimate. He is a high skill ceiling champion, which is to say he has the potential to be gamebreaking, but he can royally screw up your teammates if you make a mistake. But that's just something you need to come to terms with. You're going to make mistakes. Hopefully with time you will get better and learn when to use your skills more effectively. You just need to take this mistakes with, "Hey, I *!#ed up, but know I know not to do that." Obviously do NOT start him in ranked. I would suggest getting some team builder or blind pick games under your belt before you even touch ranked.
Honestly, I think he works in any team composition. If you have tanks on your team, you can afford to build a little AP, but I wouldn't go crazy. His AP scaling just isn't that good. If you don't have tanks (hopefully you have some sort of a frontline) building full tank is also effective. Get a 
, get a 
. I really like 
because it gives you just that much more utility. He works in almost any team composition because of his widespread utility.
I generally start with W at level 1. I give a few shrines to my jungler (unless they're like WW where they have good sustain) and I place the rest next to my tower. Once you hit level 2, you become an amazing poke lane bully. AA with your meeps and Q the hell out of them. You can free mana from your chimes that you collect. I generally try to keep at least 100 mana. Shrines are expensive and eat up a lot of your mana, so don't place them unless you have some chimes around, you want to have enough for using Q. You should really never go OOM as Bard because of chimes.
I hope this gives you somewhat of an idea about Bard. I've got to cut it short, because I'm actually leaving my office and heading home. Let me know if you want some more info and you can definitely add me in game if you like.
Have fun!
Epic early-game tower-diving.
Surprise Baron/Dragon steals.
Ulting the adc as the enemy team tries to peel for them, forcing them to abandon their ally.
Never pick Bard if there's a chance that you can stop their ults with yours.
So never pick bard with
Catch comps. All day. Lee just loves what bard brings to the table. Speed, wall hops, and stuns on walls, which are coincidentally easier to land in the jungle. Not to mention the ability to stop counter ganks from a mile away.
Coop vs AI
I think everyone already nailed it. When you get enough charms he actually has an insane ability to chase and lock people down. That is to say you will not be able to get away from him once he's on you.
Now if you're team is awesome that means if you catch people out they die. If your team is bad and they don't follow up on bards CC... well, I guess that goes for any support. Only difference in regards to Bard is that he is basically all CC. You do a lot of damage with meeps, but they eventually run out.
So... a lot like a Thresh. You set up the kill and yet are rarely ever able to kill someone solo. Your main goal is to get in other peoples away and tank them. At least that's been my experience so far.
Above Average Early Game Support Strong Middle Game Support Depends on Chimes Late Game Support
Once Bard has a Level 5 tether and a Level 3 shrine, he is pretty powerful. Pick him against matchups that are strong at trading from a range, such as Thresh, Corki, Caitlyn, and Sona.
Bard is really good in a team with Caitlyn. Landing a double cosmic bind lets her use q for full dmg which is quite slow to cast.
Bard's ultimate is amazing with Talon's ult. Freeze the whole team with your ult. Talon uses his blade thingy, he quickly moves+ flashes ACROSS the zhonya'd enemy team and BAM he hits everyone for full dmg.
Champions with great synergy with Bard's ult: Heimerdinger's turrets, Maokai, Akali, Jarvan, Kalista, Jinx's chompers, Teemo's shrooms, Cait traps, etc
In general, Bard has great synergy with comps who have a dash, allowing them to make full use of his ultimate to catch fleeing enemies or avoid golden freeze.
I play Bard a decent amount actually, and from what I've seen WeFlyNoLie is right in that he is a power amplifier. I think you definitely need either a strong adc laner or a strong jungler in order for him to be effective in lane. He's great at helping either one but you need the other to either be able to control the jungle or lane while you are away.
