(If you're holding your cards, you can brush them against the table behind your bet.) Imagine that you're making a slight, subtle, upside-down 'Come here' motion, and you'll get the idea. When you want another card, say, 'Hit me,' and make a brushing or scratching motion behind your cards. Always keep them above the table, in plain sight. Never touch them with two hands, and don't handle the cards more than necessary. Casinos prohibit this to prevent players from marking the cards in some way.
The dealer doesn't always count your bet ahead of time, so he might think you're adding more than double to your bet when you mix the two together. If you're doubling down, place the additional chips next to the original chips that you bet, not on top of them.The dealer might think you're trying to sneak extra chips into your bet because you have a good hand. Once you've place your bet, don't touch the chips.
