Casino 21 doesn't change too much from house to house. The same basic strategy applies whether you're playing online blackjack or in an illustrious casino on the French Riviera. The whole idea of the basic strategy is to minimize the house advantage as much as possible without counting cards.
Once you introduce card counting, as well as other advanced techniques such as shuffle tracking and dealer tells, it's possible to turn the odds in your favor. Of course, if you're caught counting you're likely to be asked to leave--and that's the more polite approach. Card counting gives the player a fairly good idea of how many face cards have been played and, by extension, how many are left in the deck or shoe.
Newcomers to Casino 21
If you want to play casino 21 and need to know just enough strategy to keep afloat, your best bet is to begin with tables and charts. These will tell you exactly when to hit, when to stay, when to split, and when to double down. It's important to remember that all these decisions are also based on the dealer's face card (or what the dealer has "showing").
You always want to split aces should you be lucky enough to receive a pair, but what about two fours or two fives. Do you split those? Do you double down on 11 even if the dealer has an ace showing? These questions can be tricky, but if you stick to the basic strategy every time it's possible to come out with close to 50-50 odds, whether you're in an online casino or at the Excalibur.