A successful is that you buy bitcoin with lower price and sell them little higher and get some benefit from it.
but every exchange site have different exchanging system you should know that how they works. localbitcoin is a different type of site, it is actually a exchanging site but exchanges are not controlled by site's staff, there users can set their own price and rates, so try to nearest person you and try to cheapest rate for bitcoin.

Tip: if you trade in bitcointalk forum, make sure to user escrow for success your trade.