Zedruu give them Hell (EDH / Commander)

Be generous and help your co-players with (sometimes) nice things.

Gifts: Some cards are explicilty made for granting them to other players. Feldon makes things that can be given away - his ability forces you to sac the tokens, but you can't if you do not control them anymore ;)

Give and Take: you can give other players your stuff, take theirs, exchange between other players or them and yourself.

Evasion and Recursion: Sometimes, your co-players will want to kill Zedruu (why would they want that?). So you give her shorud, hexproof or make her effectively indestructible. Hanna helps getting your nice gifts back from the graveyard :)

Defense: At some point, a hand of 20 cards and 60 life might look scary, so be prepared to defend yourself. Even better: don't let them attack at all.

Removal and Counter: Don't control the game too much. Just use it for defense or to bring the win home. Perplexing Chimera can be a big problem, so play it wisely.

Wincons and Helpers: At some point, Library of Leng (and Reliquary Tower) will give you a huge hand. It's not necessary but helps a lot. Psychosis crawler then kills most co-players (or opponents at that point?) in one or two attacks - just make it unblockable. If you dominate the board enough, draw your library and win with Jace or Lab Maniac. Niv-Mizzet will usually ping your opponents to death in 2-3 turns.