Place the 6 or 8 is considered one of th better bets on the table. If you really want to have the bet 'working' during a come-out roll, tell the dealer and he will make it as being 'on.' If you already have a bet on the table during the come out roll, it is assume to be 'off' - that is you can't win or lose no matter what the shooter rolls. However, it's generally consider bad form to make a place bet during a come out roll. You can make or take town the bet during any betting period. If you want to stop betting the number, ask the dealer to 'take your bet down' and he will hand back the $6. The dealer will pay you the $7 and leave your $6 up continuing to bet the number. If the shooter rolls your number, you win $7 for every $6 you bet. toss more than you need and the dealer will give you change. 'Give me $30 on the 6' 'Give me $12 each on the 6 and 8', etc.
You place bet should be a multiple of $6 ($6, $12, $18, etc.) You make the bet by getting the attention of your dealer, lightly tossing your money in his/her direction and announce your bet. The most common bet is to 'place' the 6 or the 8. There are several ways to bet the 6 and 8.