I charge an hourly rate of $25 which is very low by industry standards, but I do have a minimum charge of $125. The reason for my minimum charge is that any photo shoot I do will have at least four components:
1. Travel time to and from the shoot billed at a minimum of 1/2 hour each way.
2. Set up and take down time of my equipment. The more technical the shoot, the more equipment involved, the more time needed for this component. This is also charged at a minumum of 1/2 hour (each) for set up and take down.
3. Photo Shoot. Charged at a minimum of one hour.
4. Editing. This is probably the greatest variable as some shoots are going to require minimal editing time whereas other shoots will require hours of editing, primarily dependent upon the required number of shots. This is charged at two hours minimum as this also includes getting images on to the computer, sorting, classifing, editing, and transferring images to different media such as CD/DVD or Dropbox or similar service.
Longer shoots could also include a Meals/Accomodations component as well. All charge components would be discussed before a shoot is undertaken.