Economic interest groups are formed to protect the economic interest of its members.Trade organizations and labour unions are examples of groups formed by economic motivations.Activities include meeting with, calling, faxing, or writing government officials and staff as well as giving testimony or speaking at public meetings, submitting position papers, engaging in relevant lawsuits, and writing amicus curiae (friend of the court) briefs—statements written by nonparticipants in a case that supports the legal argument made by one of the participants.
The public Interest groups focus on issues that concern the general public such as social, health and environmental.
A special interest group is a group that, in pursuit of its goals, lobbies for government assistance or against government interference. However, concerns about the disproportionate influence of interest groups, as well as the unbalanced influence among those groups, remain despite the passage of various laws governing lobbying and the participation of special interest groups in campaigns.
founding fathers created separation of powers, checks and balances, and federalism in order to keep such groups from gaining too much power or influence.
Basically, all groups regardless of whether they are motivated by economic, professional or public interest make use 4 major tools to achieve their goals: lobbying, electioneering, litigation and demonstrations.
However, the tools utilized by an interest group at any point in time depend largely on issues such as its financial capability, size of members, and its level of organization.