As part of my job I help to mentor members of the public unschooled in the use of even the most basic of IT skills, using government approved teaching software (accessible through the library computer system).
Tip one, Remember they are not IT experts, so avoid the use jargon. Try to use everyday terms and avoid tech speak. Speak clearly and concisely, and never ever get flustered by their lack of tech savvy.
Tip Two, Be conversational, try to be a friend as much as a tutor. Mentoring is not teaching, it is more personal and informal.
Tip three, Remember they (most likely) know very little (if anything) about IT, take it slow and calm. Remember they are there because hey want to be, they want to learn IT they just have no experience of even Turning a PC on.
Tip four. Let then learn in their own time, never try to push the pace, and let them decide the order they wish to learn, a 90 year old does not need to know how to look for jobs online.
Lastly, Some people are not cut out to learn IT, no matter how hard you try. Accept this, not as a failure but as an opportunity. Just try to make the lesson as interesting and fun for that person as you can. They may not go away having learned IT, but they will have gone away with a good impression of you, and they may tell their friends.
Mentoring is about making a subject less daunting to the end user. Your job is to encourage their desire to learn how to use a computer, and how best to interact in the information age. Encourage them to enjoy the experience, to see computers as a tool and not an a monster.
You will note I have left out knowing about the subejct, I think that if you are mentoring people in IT skills it’s safe to assume you posses those skills already. If you do not then there is only one tip, do not do it.