Mainly adding to this for the programming motif. When someone asks how my algorithm works, I struggle to first figure out at what level I need to simplify the explanation, or use analogies. I know that if I simplify it too much s/he will feel I am talking down to said person. If I don't simplify it... glazed eyes..., but I do not see any portion of it as complicated, so I do not know where a certain person will get lost. Most of the time, I side step the question and just show them how to use it.
Regularly, I have to document workflows and setup instructions, and I always have to assume they know nothing. Some of it is that I really don't know how technical people are going to be and whether they can fill in the blanks (there are a few folks that I know I can write very basic outline and they can fill in the blanks, but that is like 5% of the people I deal with) and some of it is that I have to assume they are not native English speakers. So often times I really write it in simple terms... and find people often copying snippets of what I wrote to supplement their documentation. For instance, instead of saying "edit the file and make change xyz", I found I have to write "type 'vi test.txt' and then move to the line that contains xyz..." even for documentation that is directed just for my team.
