It's not just you, it's pretty hard for me too.
Tips for the uber newbs from a slightly-experienced-newb:
When the opponent has only two cards, the absolute max they can have is revealed card+11. This means, say, they have a 7. The absolute max they can have is 18. You should try to lead or equal the number. But revealed card+10 is more likely a stopping point, as As are not extremely frequent (at least, I think). Still, prepare for the worst.
The place to stop is 16. Around here, your chances of getting a good card just drop significantly even with high luck. At about 18, STOP. Because your chances of getting a good card, even with great luck, are horrible.
Don't abuse your luck. Just because you have luck, doesn't mean it'll save you all the time, so only use luck-intensive card selecting when you know your opponent has a higher card.
Cheating is a bad idea in my opinion. When you usually need it, it'll usually fail. You'll just loose karma and your potential (sucky) reward.
If you have a 10 or lower, always pull out a new card; you'll never go over because the absolute max each card is 11 on an A.
Count the opponent's cards. If they equal 21 or something above and there's more cards, they've definitely gone over. If their last number is big, like 10, after pulling a lot of other cards, they may have gone over.