Your objective as expanded upon in "official" 8-Ball rules, (whichever league, tournament or local rules are used) is to pocket your set of object balls numbered 1 through 7 ("lows" or "solids") or 9 through 15 ("highs" or "stripes") before pocketing the 8-ball on a call shot.
**A lot of arguments are created over sinking the 8-ball on the break. Do you lose or win if it is pocketed on the break? Some local "rule books" say it's a loss but many disagree with this mess.
In many places the eight on the break is a win. And it should be a win--it means you risked breaking the balls hard enough to scatter the 8-ball also.
But where your local rules state sinking the eight is a loss, make sure your opponent racks tightly. The opponent should always rack tightly in all games, but a tight rack helps ensure that the 8-ball wouldn't move much on the snap. Referees who have many 8- or 9-balls sink in those games will come under scrutiny for improper racking!**
Calling pockets for individual billiards shots where local 8-Ball rules allow adds flexibility--whether a ball goes straight into the pocket, zooms around before sinking or flies through the air to the hole like a basketball to the hoop, you retain your turn.
To begin the game, make an open break, smashing the balls apart. Although it is debatable whether breaking 8-Ball hard (or breaking at all!) is a wise idea. Your turn continues if a ball is pocketed on the break, if not, your opponent starts their turn.
The fairest way to proceed is to have an open table despite what has been pocketed. Even if you've sunk three solids and no stripes, you must make a call shot after the break to ensure solids.
Once your set is determined, you must "play clean" hitting an object ball, one of the balls from your set of stripes or solids, first on any subsequent stroke. Failure to strike your set first (or striking one cleanly followed by subsequent failure to drive at least one ball into a pocket or rail) yields ball-in-hand to your opponent.
Ball-in-hand is awarded following any cue scratch. With ball-in-hand one measure designed to speed play, a second is that object balls illegally pocketed stay down and are not returned to the table. Technically a player could use their turn to push an opponent's ball straight into a pocket!
BCA rules, which pave the way for enjoyable play, stipulate that a scratch on the 8-ball is not a loss of game unless the 8-ball pockets on the same shot. (This unusual rule was set to end long defensive struggles where players were afraid to disturb an 8-ball close to a pocket.)
Pocketing the 8-ball in the wrong pocket (different than the called pocket) or on any stroke before your set is cleared is an immediate loss of game.
Consider classic 8-Ball rules as they apply to open table strategy on the next page, since few of your opponents will!