There are a few ways: 1. Confidential informants. The police write in the warrant application they have a reliable confidential informant that has seen and knows abouf a dealers activity 2. read more
The government possesses vast technology designed to detect and gather evidence of drug conspiracies. Nevertheless, by far and away the most common method of gathering evidence is the old fashioned way- from snitches and rats ("confidential informants" and "cooperating witnesses"). read more