How do interest groups influence public policy?
Raise awareness of new policy issues, lobby for their preferred policies, provide money for politicians campaigns, try to engage the mainstream media and social media to support their causes.
Interest groups use a number of strategies to influence government policy to favour their beliefs and goals. Industry groups often have the financial resources to influence politicians by making donations to their re-election campaigns - this creates an obligation by politicians to help the industry groups out at some later date.
Industry leaders and lobbyists will also try to meet directly with politicians to make their case. Industry often uses the argument that jobs will be lost and/or the economy will go into a slump if their preferred policies are not enacted. Scare tactics that are usually not entirely true, but may have a grain of truth to them.
Environmental groups do not usually have lots of money to "buy" politicians, so they tend to rely on engaging the media to indirectly put pressure on politicians to act. Social media has become very effective in engaging younger people in environmental causes, who in turn put pressure on politicians to act.
Scientists will often release research studies with the hopes that politicians will take these findings into account when they develop policy. The medical community, and especially doctors, have a high credibility with the public and will some times write letters to politicians signed by hundreds of health care professionals - again, in an attempt to move politicians towards their views.