Short version is - pick a group of people to organize. Figure out exactly who is in that group. Talk to all of them, one at a time. Recruit the ones who already know what you're doing. Tally how much support you have. Either convince more people, or try a thing that's possible with the level of support you have. Check how much turnout you get. Convince more people, try a thing that's possible with the level of support you have, check results. Repeat.
Jane McAlevey's book is good. Her interview at Current Affairs is shorter.
The one good Chapo episode. I like the spreadsheet.
Short version is - pick a group of people to organize. Figure out exactly who is in that group. Talk to all of them, one at a time. Recruit the ones who already know what you're doing. Tally how much support you have. Either convince more people, or try a thing that's possible with the level of support you have. Check how much turnout you get. Convince more people, try a thing that's possible with the level of support you have, check results. Repeat.