The betting public has an image of blackjack as a beatable game, and that has helped the game attract the lion's share of table play. It's really only beatable for the select few who have the knowledge, discipline, and bankroll to be effective card counters. But even players who don't count cards can narrow the house edge to less than half a percent if they'll just take the time to learn proper strategies for hitting, standing, splitting pairs, and doubling down.
The task, when confronted with something more complex like variations in betting, is to grope for some approximate representation, conceptually as simple as the insurance structure, in order to avoid the impossibly lengthy computer calculations which would be necessary to analyze all possible subsets of a blackjack deck. Ultimate justification of the following method will be deferred to the Appendix for the mathematically inclined.
Unfortunately, most casinos don't allow you to exit and re-enter a game at will. Sitting at a table and playing a few hands, sitting out a few, then jumping in and playing again is a sure-fire way to draw attention to yourself.
A less obvious way to play is to back-count, which means standing behind a table and counting cards until a favorable situation arises, then jumping in with a big wager. This approach was first suggested by Thorp and is now sometimes referred to as "wonging." Back counting makes you less obvious in your avoidance of the negative hands at the beginning of the pack while you wait to play only the positive hands thereafter. As soon as the deck sours, you leave to find another table.