1. Go to Google
2. Type in the search strings:
Outdoor Portrait Photography
or
Portrait Photography Outdoor
or
any combination of those words or others you can think up.
3. Read
4. Read read
5. Read sum MORE!
6. Test shoot
7. Basics:
Reflectors, diffusers, and Gobos.
White sheet, blankets
Props: Lunch basket was a good suggestion, wine glasses, hats, towels, etc.
18% Grey card
Set your white balance, or at least see if it gives you better results than auto
Get in close and fill up the frames. Remember that the subject is the focal point, not extraneous things like feet, people walking by, Ferris wheels, beer cans, etc.
8. Take lots of shots and bracket them.
9. Settle on one or two compositions and then work them like crazy for lighting and angle.
10. Be prepared to do it again. Tell your subjects that it is quite possible you'll need to do it again.
11. Tell them that your camera works better when there are small bathing suits because of its "outdoor skin tone reflection" processor, which gets confused unless it sees as much cloth or skin as possible.
12. If they buy #10, please post shots for review.