They find out who the officials are who are hurting for money, who have a drinking problem, who like to womanize. They have a way of detecting the weaknesses, and they attack it.
Drug traffickers use intermediaries to develop friendships with certain officers and agents.
Some will try to set up dates for the agents. One federal law enforcement officer in San Diego, Calif., who has worked with Mexican police described several nights out with Mexican officers in Tijuana, where the police would often have free drinks in bars the officers acknowledged were run by affiliates of a drug cartel. Once the go-betweens determine that an agent is ripe for a bribe, money is offered. Usually, drug traffickers are careful to gradually ask for something in exchange, like waving a load of drugs through an inspection booth or persuading other officials to look the other way. Sometimes, the smugglers demand that the official help move the drugs over the border or drive the loads to northern cities.