When I usually play Canasta, we usually just sit down at the table, and the person you are sitting across from becomes your partner. I think this is usually the simplest method. The Canasta rules from the US Playing Card website suggest drawing card to determine partners. In this case, A is high, 2 is low and Jokers require the player to draw a new card. If two players end up with the same value, you can either go based on suit or have the players redraw. If you go based on suit, spades are high then hearts, diamond, and clubs are low. If a higher card still can't be determined the players should redraw. The players with the highest and second highest cards become partners. As mentioned before, partners always sit across from each other.