The penalty depends on the discipline and event rules. WPA's basic shot sequence is to contact the legal object ball first, then make a rail contact or pocket a ball. Always confirm the exact game rules before play.
Frequent violations
Typical fouls include striking with something other than the tip, double-hitting or pushing the cue ball, touching a ball with hand or clothing, shooting before all balls stop, and sending the cue ball off the table. Playing out of turn or contacting the wrong ball can also be a foul.
After a foul
Wait until every ball stops and do not move them yourself. In many games the opponent receives cue-ball-in-hand, but placement rights vary by ruleset. If the call is disputed, mark the position and ask the referee.
Preventing arguments
Agree the game, announcements and foul procedure before the break. In a club, use a current printed rule set rather than an isolated video tip.