What are common tactics used by interest groups to advance their agendas?

Interest groups try to advance their agendas by influencing decision makers.  They identify people or organizations that have the power to give them what they want and then try to make those people listen to them.  They use logic, data, and personal stories to try to get the decision maker(s) to identify with and care about their issue.    But, often a good argument is not enough.  Issue groups often try to find out what motivates people and use that motivation to get the change they seek.  For example, if an interest group is trying to influence a politician, they will try to convince the politician’s constituents to care about their issue and to let the politician know. They will also try to get coverage in the media. 

Special interest groups have many ways to accomplish their agendas. They can organize mass support for and only choose to support candidates for office who support their agendas. They can also lobby politicians directly in order to make their message heard. Another way that special interest groups can get their message out is through advertising.  
One example of how this worked in history was the work of Wayne Wheeler of the Anti-Saloon League. Wheeler organized industrialists and church groups to give money to support Prohibition. These people voted in blocs for candidates who would support the Volstead Act. Even if a candidate personally drank, he voted for the Volstead Act to avoid the wrath of Wayne Wheeler's special interest group. The Anti-Saloon League also spent money on advertising, including campaigns during World War I that tied alcohol to the unpatriotic waste of grain and the beer industry to German interests. While there are more contemporary interest groups, the Anti-Saloon League was one of the more powerful of its time.