Upon identifying a balk by the pitcher the umpire will announce loudly, "That's a balk!" and point at the pitcher. If the pitcher immediately delivers the pitch, the umpire will allow the play to develop as a balk call is a delayed dead ball call. If the pitcher does not immediately pitch, the umpire will call "Time!" and make the appropriate base award.
Professional umpires are usually advised to yell "That's a balk!" very loudly with the intent to startle or freeze the pitcher. Once the pitcher hesitates time call be called and the play is dead.
Should the pitcher deliver the ball, or throw to a base, the umpire must compare enforcement of the balk against the outcome of the live ball play. For example, if the pitcher delivers and the batter hits a home run, then the balk is ignored and the play (the home run) is enforced. The determination of whether to enforce the play or the balk belongs to the umpire, not the offensive coach.
Consider this example: R1 on 2B. A balk is called and the pitcher delivers to batter who grounds out to second. R1 rounds third and scores on a close play, scoring the winning run. The Penalty section of Rule 8.05 reads: "PENALTY: The ball is dead, and each runner shall advance one base without liability to be put out, unless the batter reaches first on a hit, an error, a base on balls, a hit batter, or otherwise, and all other runners advance at least one base, in which case the play proceeds without reference to the balk." In the situation described above the runner advanced two bases, but the batter did not reach first base. Therefore, the balk must be enforced, R1 goes to third and the batter is returned to the plate.
Here are some balk nuances:
1. If a balk is immediately followed by a wild throw to a base that permits all runners to advance beyond the base to which they would be entitled by the enforcement of the balk, the balk is ignored and the ball remains live. Take for example R1 on first. Pitcher balks and throws wildly to first. R1 advances to second, then tries for third where he is thrown out. Balk is ignored and out at third is enforced.
2. If only the runner advances to or beyond the base which he is entitled because of a wild pitch after a balk, the balk is acknowledged and the pitch is nullified. The batter will resume the at-bat with the same pitch count as before the balk was committed.
3. If the play results in a fly ball out, the play is dead, the pitch is nullified, and the balk penalty is enforced.
There is an old saying, "See a balk, call a balk." In other words, make sure that balk is obvious, or don't call it. Once you call it, call it loud enough to startle or freeze the pitcher. Do this for your own protection, otherwise you could have a sticky situation with an upset coach and confused fans.
*EDITOR'S NOTE: under NFHS (high school) if you call a balk, it is an immediate dead ball.