Summarize:

Hits (also called base hits) are simply the sum of singles, doubles, triples, and home runs. This statistic is easy to find online for professional players. You can use the statistics for a season, a whole career, or any other period of time you're interested in. Just make sure all your statistics come from the same time frame. This is the number of times the player has made an attempt at an hit. This does not include walks, hits by pitch, or sacrifices, since these do not reflect the batter's offensive skill. The answer tells you the battering average, or the fraction of the time that a batter turned an at-bat attempt into a successful hit. For example, if a player had 70 Hits and 200 At-Bats, his Batting Average is 70 200 = 0.350. You can read a batting average of 0.350 as "this player would expect to get 350 hits in 1000 at-bats." Batting averages are almost always rounded this way. When a baseball fan mentions a batting average of "three hundred," she means 0.300. You can calculate batting averages to four or more decimal places, but this doesn't have much use beyond breaking ties.
Find the player's hits. Find the player's at-bats. Divide the number of hits by the number of at-bats. Round to the third decimal place.