There are many books on teaching adults - perusal of one or more will help.
However I suspect your main role is as facilitor - ie showing others where information is and how to access it, showing good examples of family trees etc and being clear in your own mind why these are good (eg use of checkable refs, documentation) - as in any adult teaching your enthusiasm must come across as well as your preparedness to learn from your students.
If you want an example consider the difference in approach between David (the apprentice) and Hans Sachs in teaching the knight Walter the art of Mastersinging. The first went thru a long list of items that had to be learnt - the latter listened to the pupil and built on what the pupil could do - finally showing that there was still much to learn and that even the teacher didnt know all the answers