Follow the build and you will be successful. Not teaching how to play the champions, but it's how you use them.
Where the ward is in the picture, is where you put the boxes. (Right in front of the wall on the right is where you stand). Put as many boxes as you can and get lizard without smiting when it spawns. If the other team decides to break those boxes, you need to be prepared. Have your teammates stay behind the wall same was as you do and when the other team comes in, you KILL THEM. If they come and break the boxes (dying or not), you can get the lizard with 1 or 2 boxes and smite. If you kill lizard without smite, go to the camp on the right or left, whichever side you're on and kill it. Before laning phase, tell your teammates to harass the enemy down HARD so at lvl 2, you can gank with lizard buff easily and kill.
Start with Consume. Stay in the top left or right jungle. Stay in the bush until the minions spawn at 1:40. It's normally wolves, but it can be two golems. If it's wolves, attack them one or two times and consume and run away to the 2nd camp on the top. Wait till it spawns at 1:55. Wait for your consume and then fight it. When your consume is up, you smite the big one and consume. Walah! Instant level 2! Then you go to the 4th camp which is the small ones. Kill them all. Then finish the mini creeps on the 1st camp and the 2nd camp. By now your smite should be up. Smite and Consume the big one and kill the rest. You're level 4! Guess what time it is! It's time to gank... Let's look back to the 1st camp at the start. If it's two golems, you attack one until it's around 500 hp and consume.
This is how " I " play these champs so don't tell me blah blah blah shouldn't do this shouldn't do that. I believe DPS Nunu is the best at late game when he's becoming useless. Movement speed and attack speed slow nuke ball + attack speed + movement speed buff, definately DPS. Shaco is not a bad champion at all in 3v3. Stealth/Assassin/Clone/Fear/Free box wards/Wall jumping If you're getting raped sometimes as Shaco, remember you have your ultimate. Sometimes when you're like 50 hp and you're about to get hit by a turret and die, use your ult and it'll take it off. For Shaco, at the end, you can sell Wriggler's and get a Gunblade and sell Berk greaves and get probably a swift boot or merc treads. Important note: if you don't want to get raped as a Shaco, get exhaust IF only they have burst champions like Annie, Tryndamere, etc.
Not sure who to ban in 3v3? Here's some : Dr.Mundo, Singed, Sion, Nunu, Jarvan, Gragas, Renekton, Xin Zhao, Tryndamere
Secret Jungling Tip
Ever seen team jungling? It's when two players with smite are jungling to level 2 instead of having one jungler jungle the whole thing. I'll get to that. You should only do this when you have a Nunu on your team. The second player should be a DPS that can heal. For example; Xin Zhao, Tryndamere, Udyr. So first of all, you have a Nunu with consume. You finish the 1st camp on top without smiting anything. Wait for Nunu's consume to be up. Nunu consumes the big guy on the second camp and one of you smite(make a choice before you start doing this). Finish the rest and move on to the 3rd camp. Nunu consumes again and the person with smite up now smites it. Finish the rest and you're both lvl 2 and with one buff each person! How cool is that! If you're Xin Zhao or Tryndamere you can probably go through the wall back to top lane and start playing normally or maybe kill. Nunu will finish the 4th camp and maybe go B or gank.