Go to the political party of your choice's monthly meeting. Each party/state has slightly differen't rules, but the major parties have a local chapter in every state. Speak up when the chance is offered / on topic (it won't be everytime). This is where you learn who is planning on running before they announce - in enough detail to have an informed opinion on if they are good. that is where you go to find out how to help those who are running win.

everything else is noise that won't change much. Get good people elected. Knocking on every door will turn out enough votes toechange election results in your area.

don't fall for one party good. all are badin different ways. Find one that mostly you can support and reform it. Small issue voteres who get involved change how the party acts (in part by ensuring people who agree are on the ballot, in part because those who do the work get long conversations with the people they support - thus changing how congress thinks).