tips

Well, what kind of photography are you wanting to do?  What is the goal of your shoot?  Are you shooting a model or someone who is paying you?

We tend to do that a lot here

Another question, haha: When you say "evening shoot", what time are you talking about?

With the 18-200mm lens, be careful not to delve too much into the 18mm range when doing a head shot. I've been guilty of doing it myself and, let me tell you, it's not kind to noses!

I think the first thing you need to do is have a clear goal in mind of what it is you're going for when you get there. "We're going to shoot _______." No matter what it is you should be making her look her best. That's a concern that needs to be raised later in the process.

So what are you going to do? Swimsuit, lifestyle, formal portrait, candid, woman in nature, woman au' natural...etc? Figure that out first. Set an easy simple goal.

Lighting. First you have the sun, and then you have a way to reflect it. If you have a flash I'll bet you only use it on camera; don't. Stick with a reflector for now. Make sure you have someone to hold the reflector. Study the light. Give her eyes a break every few shots from the reflector too, they can be a killer in bright light.

Look at her face and body shape and think about what angles look good for her, and what you don't want to stand out. People really do have a good side for photographs.
Look for sticks, telephone poles, and other things in your background that will seem to grow out of peoples heads in a photograph.

Have her bring a bunch of wardrobe that goes toward your goal. Pick a small amount of it carefully. Avoid big bold patterns unless your selling them. All black and all white clothing can be a little harder to expose for so find something in between.

Have fun and enjoy the process. But don't forget that everything in the frame is your responsibility, including what the model does.

Thanks all

It's a trick to get lighting patterns like butterfly, loop and modified loop with natural light.  I am NOT saying it can't be done.  I would focus right now on knowing the difference between short and broad lighting and focusing on getting lots of light in her eyes.  If you are in open shade, which you will be for part of the shoot as the sun sets I would find your main light (I use a business card folded in half if it's not easy to see) and turn her toward the main light and use the reflector to bounce light up into her eyes.

Watch your backgrounds, I like to keep them simple, unless the scenery is part of the story (like a wedding chapel in the background, or a beautiful landscape with the person as part of it usually smaller in the image).  Use that 200mm a lot.  Step back and zoom in, this will blur your background and put your model in focus which has a lot of impact.

Robert, there's no trick when it comes to SEEING what the light does on faces etc.
It's a matter of positioning either yourself and or model/person/subject and using reflectors etc.

I'm an outdoor photographer, maybe it's easier for me to see it and others who work outside a lot, it comes with practice.