I think honesty is also really important. Like don't hide or mask your politics. It means people are clear about why you're doing it, and not thinking you're some local community group, charity or political party offshoot. When chatting we always said something like, 'We're revolutionaries, we want to abolish the State and capitalism and want to do XYZ as part of that/building towards it.' Almost without exception we got a good reception to that, I mean people would often laugh and say 'you're mad' but more in a way of 'that will never happen' rather than 'I don't want that'. I think being able to explain your politics, the world, and how you imagine change happening and how what you're doing fits into that is essential. As is then saying that's the plan, but it's not a fixed program and can be worked out in the process of doing this stuff together.
One of the real lessons for us was that you're going to come across enemies (political opponents and social groupings like gangs and slum landlords) and at some point you need to be able to beat them with the ability to wield power and that's something that needs to be established quickly in order to have any credibility imo. That and listening to people's problems, being able to situate them in a wider political context and offer/enact solutions requires huge collective confidence and a lot of time and energy.
Confident, coherent and clear politics, being able to explain them to anyone easily, wielding the collective power to fix problems, and offering something appealing in the present (maybe socially as well as politically) would cover 90% of what's needed I think.
Anyway, sorry, enough rambling, back to TRANSFORM...