Baseball, like other games, is a contest to beat the other team. This is done by scoring runs, which happens whenever a batter gets on base, and runs from first to second to third and finally back to home plate, all without the defense recording three outs1. However, this entry concerns the first part of scoring runs: getting on base.
Also, if your friends are impressed by random trivia, this is a great list to memorise. It's even a Trivial Pursuit question! Most fans of the game can name five or six, but those last two or three are always tricky.
The List of Eight
A hit is recorded when the batter strikes the pitched ball with the bat and runs to first base for a single. Provided, of course, that none of the fielders catch the ball in the air or pick the ball off the ground and throw it to first before the batter gets there. On an especially well hit ball or with an especially fast runner, the hit can become a double, triple, or even a home-run. As a side-note, hitting a round ball squarely with a round bat has been called the most difficult act in sports; even the best players get hits in only about a third of their at bats.
A base-on-balls, also known as a walk, is given out when the pitcher throws four pitches outside of the strike-zone2. This is made more difficult by the batter having to recognize these pitches as being out of the strike-zone and not swinging at them. If a batter is particularly well known for being a good hitter (or if the batter following him is known for being not), the pitcher may deliberately and blatantly throw out of the strike-zone for an 'intentional walk', and all the batter has to do is stand there.
Some pitchers don't like batters crowding the plate and will throw inside3 to 'brush back' the batter from home plate. Sometimes, though, the pitch 'gets away from him' and the batter 'takes one for the team'. The pitcher might also do this deliberately, in which case he is a 'headhunter' and might start a 'bench-clearing brawl'.
If a ball is hit toward a fielder who looks like he has an easy out ahead of him, and the fielder somehow kicks a ground ball away or misses an easy catch or throws the ball into the seats, it is an error. A serious overthrow could turn an easy out into a double or triple, for example. All the batter has to do is get to first before the defense recovers, because he can still be thrown out. So in the end an error may look a lot like a hit, but the batter isn't credited with one.
A Fielder's Choice
Usually in baseball, the strategy is to get the lead runner4 out so that subsequent runners have farther to go. If this strategy results in the batter getting on base, the batter is not credited with a hit even though he hit the ball and got on base. The theory is that he got on base only because someone got on base before him.
This doesn't happen very often, but when the catcher5 gets in the way of or inhibits in any way the batter's swing, he is charged with interference and the batter gets a free pass to first base. Most often this happens when a baserunner tries to run from first to second base during the pitch and 'steal' second base. When the catcher stands up trying to throw out the would-bethief, he might get in the way of the batter and the bat, which is more the reason why this doesn't happen very often.
A Dropped Third Strike
Another rare occurrance, this happens when the catcher fails to catch the third strike in a strike out. When this happens, the batter is allowed to run to first base as though he got a hit, mostly because the strike out wasn't complete. Also like a hit, however, the catcher can still pick up the ball and throw to first for the out.
As a Pinch Runner
The eighth and final way to first base is the most commonly forgotten, mostly because it has nothing to do with the action of play. Once a batter gets to first base, by whichever of the previous seven methods, his coach can replace him with a runner off the bench. This player becomes a pinch runner. Pinch runners are used as replacement players "in a pinch" or tight situation; the original runner may have become injured, or the pinch runner may be a necessary burst of speed late in a close game.
Actually getting to first base is usually done at one of two speeds: a trot or a run. On a hit, an error, a fielder's choice, or a dropped third strike, you should run to first base. Normally, you won't slide into first base, since all you have to do is touch it and not round the corner to second and you're safe6. Sliding doesn't get you there any faster. For the other four ways, you can trot. If you got hit by a pitch, though, you're better off walking really slowly to first while glaring at the pitcher. That way he knows just how upset you are at taking a ball off the hip.
The best statistic to look at when deciding how good a player is at getting to first base is on base percentage (OBP), the formula for which is complicated. Add a player's hits, walks, and hits-by-pitch and divde that by the sum of his at bats, walks, and sacrifice flies7. Taking this to the thousandths place gives you the success rate of a batter getting on base in 1000 chances. A good hitter will usually have one around the high .300s.
The best lifetime OBP, .481, is held by Boston Red Sox slugger Ted Williams, which means he got on base in almost half of his plate appearances. Second in that list is the famous New York Yankee Babe Ruth, who reached base 469 times in every 1000 chances. In 2004, because the extreme number of times he was walked for his reputation as an amazing home run hitter, Barry Bonds of the San Francisco Giants had an OBP of .609. Actually, all three of these hitters have high OBPs because of their reputations as home-run hitting game-changers, but only Williams and Bonds have the distinction of being walked with the bases loaded, sacrificing one run to prevent a possible four.