One thing I haven't seen mentioned but hopefully is fairly obvious from what I've seen of the community is exactly that, the community. As has been said, new players want to play, and doing that with existing players of the community who are willing to offer tips and knowledge is useful.
I remember running Crusade a lot and often with new players, they generally appreciated a bit of advice about power, counters and just strategies for the map. I think a huge part of it is keeping a good positive, friendly community. Seems like it should be a given though, with most people here being here