A way that worked for us (wencp), after many that did not!
Our group, and groups before that struggled with newcomers constantly slowing momentum gained by older hands. It was like the project itself was challenging enough without having to repeat answers and explanations over and over.
It took the visit to NZ by Katie McCamant this year to finally solve this one. I guess this is stuff that has evolved since their book was printed. Anyway the system is so simple it almost isn't a system.
Newcomers, ie not quite members, after having read your hopefully excellent reading materials, and attended some form of orientation seminar, need both to get a feel for the group and to get up to speed with task work. The quickest way to do this is for them to begin attending business meetings at once.
They do so as observers: no questions nor participation in decision-making. This is spelled out to them before hand together with options for having their queries answered. Newcomers seem to take no offence by this zip up approach, as it is about the 'greater good.' In our group this process lasts for 2 meetings. At this point they become elligible to 'join', by paying a membership fee of $100. This weeds out the merely curious.
Avenues for questions etc are before, during breaks, or after the meeting, informal dropins to members homes, outings or site visits and a 'buddy' system. Newcomers learn alot just by listening, some even comment that listening in on these early meetings helps train you to listen and think before talking. This is interesting because as the group gets larger and larger, meetings become more business like and you become acutely aware that every time you open your mouth it consumes precious group meeting time.
Come joining time, the incremental investment thing is the way to go, which is all laid out in the books.