In grassroots organizing there are a number of problems that need to be worked out in the moment. There are likely other sorts of people that need to be dealt with, and in different kinds of ways, but the two kinds of people I'm talking about here are people who could potentially be beneficial to your group.
These are the talkers and the dictators.
Talkers and dictators are potentially beneficial to your group because they have a passion for the topic. That's why, usually, they're talkers or dictators. Talkers can even be beneficial in their trait of talking, it's just a matter of ensuring that this talking is directed correctly. Dictators, on the other hand, are passionate but their dictator trait needs to be altered.
Dealing with talkers is a matter of organizing procedure. Talkers like to talk, and often talk over others, or will draw out their comments at length while reitterating some of their points. Starting the meeting off with the rules of discussion, which includes a "stack", a time limit, and a talking stick is a good way of dealing with talkers. You need to be polite but firm in censoring anyone in a meeting as a facilitator, reminding them that the reason you're interrupting is because there are others who would like to speak and deserve a turn. Reminding the talkers through a 1-on-1 of the procedures and why they're important -- keeping group unity and ironing out disagreements which could lead to a malfunctioning group -- is a good precursor to productive meetings. Remind people that meetings should be as short as possible so that we can all get on with our lives and get over the boring, grueling, but necessary part of organizing.
Talkers are great in scenarios that aren't directed towards group decision making or ensuring that people's feelings aren't hurt. In my experience, talkers are great speakers, agitators, media relations people, and intellectual defenders of the more timid in the face of an aggressive talker who may be against your side. Talkers are also talkers because, usually, they're passionate, so talkers are loyal. They are a great asset to any grass roots organizing. The persona just needs to be reminded, from time to time, that others need to be able to talk too, and they can be reminded through the importance of following procedures when group consensus is trying to be achieved.
Dictators, on the other hand, I've had less luck with. Perhaps there's a good way to address dictators. So far, in my experience -- though the dictators are passionate -- their attitude towards others tends to drive people away. They expect people to follow their orders, and are upset when they don't. Usually dictators, again in my experience, are just inexperienced organizers. They're passionate, they've dreamed many good dreams, they want to reach the end-goal, but they haven't had much experience in actually organizing people on the ground without any authority to back them.
So far the best thing I've been able to do with dictators is to push them out of the group. They're upset, which isn't good, but dictators ruin collective group dynamics and the possibility of growing your group or its good repute in the community to be worth it. I've tried to show dictators what it takes to be a good organizer -- being open to criticism, not taking criticism personally, attempting to blend people's desires into a super-tactic/objective that is conducive to what you're organizing on, politeness, being willing to work before asking others to do so, working with people's schedules, being understanding of people's lives, trying to work with a quid pro quo attitude towards those with resources that could help your cause but aren't necessarily aligned with the cause -- but for the most part, the whole "working with others" aspect of organizing doesn't suit the dictator's personality as much. And without other people, you're not bound to get much done.
So, unless you're particularly awesome with working with people -- and I consider myself to be decent -- I'd suggest politely telling the dictator that they can play well with others and showing them what that entails, but tell them that the dictator attitude -- specified as a person telling others what to do and expecting others to do those things without placing work into the project and without considering their needs -- needs to go, or they do.