System Entry, iBet\n\n Select four digits and place bets on all its possible combinations. For System Entry, each 4D number combination costs a minimum of $1. For iBet, all 4D number combinations cost a minimum of $1 in total. Your prize money is proportionately divided by the number of combinations.

Some bettors will assign 1 percent of their bankroll to a unit, while others could do 2, 3 or even 5 percent. If you have a bankroll of $1,000, for example, 1 unit could be $10 or maybe $20 or even $30. If you have a bankroll of $2,000, 1 unit could be $20 or maybe even $40 or $100.

The 0  (single zero) and the 00  (double zero) are the green slots on the roulette wheel. These pockets could receive a 35:1 payout if hit straight up. If there's a split, the payout could be 17:1. This type of bet is somewhat risky, but the payouts could be worth it.

As a general rule, 0 or 00 (the latter being mostly on American wheels but not elsewhere) will pay 35:1 odds just as any other single number bet. Of course, the zero(s) are the key to the house having an edge that guarantees that they make money in the long term.