I've always assumed "the friend" just to be someone you know - doesn't even need to be a friend.

I think the reason for choosing a friend is that you're more likely to know his (or her) physical features and behavior pretty well.

But bear in mind that Charles Haanel wrote that book (The Master Key System) in the early 1900's and he didn't know about the modern media technologies of today so that's why he's recommending a real person to visualize. And, in fact, when I first read the book, even television in color was still a relatively new thing so I also used a real person for the exercise.

But these days I would say it would also be perfectly acceptable to choose anyone you may have seen in the movies or TV also...just anyone you are familiar with.

This is an exercise in imagination and visualization first and foremost rather than an exercise in friendship :)

...oh, and best to do it in your head only, unless you want your other friends to think you've gone a little bit mad as you sit there having an out-loud conversation with an imaginary person :)

Stingray's answer is good. This is nothing more than en exercise in visualization so choose any friend prefereably one you are on good terms with and even better the one you last had a conversation with. Make sure you choose a friend you like and never imagine a argument but something pleasent and suprising. The important thing here is to watch the change in manerisims and the facial exprecions for when you can visualise this and see and feel the diferance thats when you know your visualisation technique is good but dont just stop there keep practicing.

Of course you know this must all happen in your mind. See it, hear it and live it in your mind for a while and this practice will perfect your visualization.

Good Luck

This exercise not only helps with improving your imagination which is required for any kind of manifestation but also your focus. In practicing this exercise, I picked a person I had not seen or spoken in 30 years. I rehearsed (ONLY IN MIND) talking to him. To my surprise, some neat fact about the person floated in my mind as a result of concentration. He used to wear a perfume every day. This fact in fact I had forgotten totally and my brain fetched that from deep hidden memory. Other than this, Stringray's reply is perfect.

It is my inner friend my perfect being, the one who is always there when all else fails.