Some things are obvious, like pocket Aces and pocket Kings are keepers, 72o and 94o are trash. In between lies the actual decision making. The thing to keep in mind when choosing starting hands to play is that some cards can grow up into big hands, like flushes and straights, and others cannot (barring a lot of help from the board). The decision to play any two cards will change depending on whether the game is limit or no limit, where you are in position at the table, who you are playing against, whether you’re in a tournament or a ring game, etc. So the best I feel I can do here is to give some outlines, and you’ll have to hone your game through the time honored maker of men, experience.
Pairs: To start with, big pairs (Aces, Kings, Queens) are great starting hands. They are already “made hands” in their own right. You can play them from anywhere (position-wise), and should usually raise with them. You don’t want to play high pairs against too many opponents, or someone may get lucky and outdraw you by the river. A pre-flop raise designed to thin the field is usually the best bet. Jacks through Nines are iffy, they’re good cards, but if the flop shows better like a K,Q or Ace, all of a sudden a pair of Jacks in the hole isn’t so great anymore. You can play them hard (raise) before the flop, hoping to thin the field and maybe pick up the blinds. If there is a flop, and face cards come out, you’ll have to be careful. There’s a good chance anyone who calls a pre-flop raise has face cards, and may have a better pair than you now. But as far as starting hand selection, yes, play these cards from anywhere (position-wise). Medium pairs and less, say 8’s down to 2’s, would be welcomed heads up, but against a larger field of opponents, these guys usually won’t stand up. Against a hand that someone would raise with, they aren’t worth playing. That brings table position into play. If you are the last to act, you’re sure there won’t be any raises and can play them. If you are first to act, and there is a raise behind you, you’ve wasted a bet (unless you’re willing to “give it a shot” and call the raise, in which case you may be wasting two bets). Also, for hands like these to really work, you’ll need to land the third card for a set (Three-of-a-kind). You’ll land the set on the flop about 12% of the time. So, 7 out of 8 times you’ll say “Okay, I’ll pay one bet to see the flop. Oh well, missed.” and fold if someone bets. That’s a lot of missing. So when you do land the set, you’ll need to make up for all those chips you spent seeing the flop with a small or middle pair. You do that by only playing small or middle pairs against a lot of players. That way when you win the pot after hitting your set, you win a big pot. Say you play a middle pair against one or two players and hit your set, if you bet and they fold, it wasn’t worth the risk.
Suited Cards: Obviously the advantage of playing suited cards is having an inside track to a flush. So, finding suited cards in the hole is a good thing. The bad thing is that suited cards turn themselves into a flush only 6.5% of the time. And that’s when you stay in until the river, every time (which isn’t likely to be the case). So, you can’t play every hand where you find suited cards in the hole, and expect to come out ahead. Instead, play suited cards that have something else going for them as well. Suited high cards are a combination worth taking to the flop. Suited connectors (cards in sequence) are often worth playing since they can turn into a straight or a flush. A flush is a very good hand, but only the highest flush wins the pot. So, if you play 98s, and land your flush, anyone else that has a flush with the T, or the J, or the Q, or the K or the Ace will beat you. Keep that in mind if the betting gets heavy. As far as playing Ace-anything suited, remember that if your “kicker” is weak, you’re really hoping for the flush (not Aces on the board). And, the odds of hitting that flush are less than 7%. If the odds against landing you hand are that much, you’d better win big pots when your do land your hand, or you’ll be losing chips in the long run. Playing “any two suited” means you are going against the odds to catch the flush, and even then you had better hope you are the only flush holder. I recommend against playing two cards whose only positive is that they are the same suit.
Connected Cards: These guys obviously have the advantage of more easily turning into a straight. But, man cannot live on straight draws alone. You can certainly play connected cards, especially high ones like KQ or JT, but connected cards are usually a “drawing hand”, so you’ll need help from the flop to have them grow into straights. That means you’ll want lots of players in the hand, and cheap. Once again position comes into play. If you are sitting in late position and there are a few callers (and no raisers) you can call with connected cards (the more players the lower the ranks of your cards can be). But, if you’re in early position it may not be worth risking a possible raise behind you. The odds of landing a straight on the flop are little more than 1% if you have connected cards. Even if you land a four straight, you are still on a draw. Keep that in mind when choosing starting hands.
One and Two Gap Cards: Not worth playing unless they have something else going for them. A-J has something else going for it, 9-7 does not.
High Cards: Are good when you have two of them. Not when you only have one. A hand like A-7o is bad because anyone else with an Ace can easily outkick you. It also has no straight or flush potential. One Big/One Little are “trap” hands, as you are apt to spend money thinking you have a nice pair or even 3oaKind, only to find yourself outkicked at the showdown. When choosing starting hands, think of what you have, what they can turn into, what they have to turn into to win a pot. Keep in mind some odds, and judge whether the payoff will be worth the risk.
Disclaimer: Take these as guidelines, not incontrovertible truths.