Reddit mentions of The Photographer's Handbook (Third Edition, Revised)

Lighting is going to be pretty important. Prep-work really helps out. Talk to them before, and see if they can get you some examples of what effect they are looking for. There are often pretty good tutorials online that can allow you to replicate almost any shot.

The key as Tyler5280 said, is that you have to make your models comfortable, its helpful that they are already your friends, but don't rely on that to make it natural. Often the best looking shot is not the most comfortable.

Now as for actual technique, experiment! Make it clear that you've never done this before, and you welcome all suggestions. Don't use really wide angles unless you want distortion, but otherwise go for it. I personally use a 50mm f1.8 for most portraiture, and its a pretty good combo. Since you have a 18-55 zoom, your f-stop will not go that low. One thing that might help, don't shoot on the same line as your subject. If shooting the face, shoot from slightly below, and slightly from an angle. Take a look at most head shots, you'll see what I mean.

Phew, this is a long one.

I've included a link for the guide that I personally recomend. It's a bit outdated on equipment, but the technique and composition won't ever go out of date. Its $4, and worth many times that amount. I'd buy it used, since who cares if it's a little beat up. There is a chapter on every type of photo you'll ever try to take, and a fair bit on set up and preparation for any shot.


http://www.amazon.com/gp/offer-listing/0679742042/ref=dp_olp_used?ie=UTF8&condition=used

I have this: http://www.amazon.com/Photographers-Handbook-Third-Revised/dp/0679742042

It's not very useful with things like exposure, and surprisingly it completely glosses over a few important things like the zone system or even really how to deal with exposure, but it's a good general-purpose reference manual for almost everything related to film photography.

This is where I'd start. I still keep my copy on my nightstand and go back to it constantly.

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https://www.amazon.com/Photographers-Handbook-Third-Revised/dp/0679742042