Decide what you want the politician to do. You cannot offer anything that might be construed as an attempt at bribery. Add their name to your cause to raise the profile. Approach other politicians on your behalf. Speak up for your cause in the relevant assembly - the council chamber, House of Commons, European Parliament.
Politicians have special interests.
MPs can be members of All-Party Groups or departmental committees, where they can raise your issues. Help get your messages in the media. MPs can create interest by using parliamentary devices such as the Early Day Motion, a Parliamentary Question, an Adjournment Debate, or making speeches. Council leaders can change the council's spending priorities or services. Ministers can instigate changes in the law.