Pot size is almost always the most important factor to consider when evaluating any poker decision. Poker hands have value that depends directly on the size of the pot. If you flop a royal flush in a $10 pot, bet, and watch everyone fold, hitting your amazing 649,739-to-1 shot turned out to be worth only $10. If you flop a gut shot in a $220 pot, your meager draw is worth about $20, twice as much as your monster hand made you. To make a decision to raise, call, or fold, you should know the value of your hand; you cannot know that without first considering the size of the pot.
Pot odds are the odds the pot is giving you for calling a bet. If there is $50 in the pot and the final bet was $10, you are getting 5-to-1 odds for your call. It is essential to know pot odds to figure out expectation. In the example just given, if you figure your chances of winning are better than 5-to-1, then it is correct to call. If you think your chances are worse than 5-to-1, you should fold.
The concept of money odds is often confusing to beginning poker players. It's really not that difficult: At any given point in the play of the hand, there are three sources of money, and each needs to be considered separately. There's money that's already in the pot. That's called "pot odds." There's money that's going into the pot in the current betting round. I call that "bet odds." And there's money that will be going into the pot on future betting rounds which is called "implied odds."
The big problem with restricting calls to a pair or better is that you'll be throwing away half your hands at a cost of one ante bet per hand. Of course most of those hands would be losers, but some wouldn't lose because the dealer would fold. That's where the house has its edge. The casino always makes you call or fold first. This guarantees them about five percent of every dollar wagered. Calling with an ace and king in your hand reduces the house edge, but it substantially increases the action (total amount of money wagered). If you're willing to put more money into play, this is the best way to go. See the sidebar on this page. But remember, strategy will only reduce the house edge; it won't eliminate it. People who don't play the more aggressive ace/king strategy should fold anything less than a pair and call any pair or higher.