Optimal Blackjack strategy ??

[DCWildcat]

That would be known as a basic strategy card. If you get the correct one for the game structure (see above post), it'll tell you the best strategy to take to minimize your
-EV situation.

Some casinos sell them in gift shops, others don't. Some would prefer you know less and take more -EV, some are just generally more relaxed, and some thinks they'll help keep you in the game longer making it more +EV for them to let you use them.