Start at the lowest limit available. If you like long games play the MTT SnGs, otherwise go single tables. Personally I always choose the 6-max games because there are far too many monster
hands coming up at the full ring tables, and it's easier to play the situation and the players rather than just having to focus on cards and hands.
That said, I don't usually play SnGs. I far prefer 6-max cash games. Easy in - easy out. Multl-tabling is a lot less boring.