There correct place to be varies from wave to wave, so there is no one correct spot to be.
Generally people new to the line up sit too far outside, bare that in mind and move further inside as soon as you have the confidence to do so.
It is true that longboards are not so easy to make steep drops on but don't let that put you off since the further in you are, the more waves you will catch and the faster you will progress. I sit with my shortboard friends most of the time and get on fine (minus the occasional nose-dive

).
Aim to be mobile, spot the waves coming and paddle out, in or to the side to put yourself in the correct position to get them. If you sit and wait in the same spot (especially on the outside) then you wont catch many waves at all.
Just get out and experiment, watch the other surfers!
edit> I am talking about beach breaks, which I assume you are surfing? Points are a lot easier to read and position on.