Casinos watch DD more than Shoes
So, start off with a little bit larger bet "off the top". I spread 1-12 at DD and I start with a 6 unit bet off the top. Also, if you play two hand only at high counts, you'll be toast pretty quickly. Most casinos have long ago figured out that one. Playing two hands in neg counts eats cards and doesn't cost too much. I play two hands at all times. There are many good posts about playing two hands over at BJ21's greenchip pages and archives. DD', mathprof and Don S. have all posted a lot about this.
The best cover for DD is anonymous short sessions and don't use costly cover plays or cover betting. Many casinos get alerted to you play when you have more than 5x your "off the top" bet. Also, if you have a big bet out just before the shuffle, leave it out for the next one off the top. It looks a lot more natural.
All of my advise comes from books, BJ21.com and blackjackforumonline.com. Remember, read all the information available and get all the money you can.
Cheers,
Paradox