Pictured below is an example of an American Roulette table. This is typical of the layout you would find in a U.S casino with the wheel at one end of the table and the layout to the side. Typically the croupier would stand at the wheel end and deal with bets from there.
A European roulette table layout sometimes differ in that they have a roulette wheel in the middle with 2 table layouts either side. Obviously with this type of layout more players can play so the croupier may get help from other dealers who help with the placing and paying of bets.
In a casino seating would be arranged around the table layouts. Where a player would choose to sit would depend on how much of the wheel they might want to view while its spinning. Or, alternatively a player might prefer easier reach across the roulette table top for placing there bets and therefore sit accordingly.
Before you put your bet on the table, make sure you know the roulette strategy that will give you the best chances to beat the casino. One of the best ones are the Martingale system.