First and foremost you need to see what they produce. A lot of photographers will try to pass off a slide show as a virtual tour just because they don't have the equipment and knowledge to do spherical panoramic images. If you are shooting/showing restaurant  eating areas I think you would need 180 x 360 tours in order to see all the way up and down.
Just my 2 cents worth................

If you want to get the best result of the virtual tour. First you need have a Nikon or Canon DSLR, sigma 8mm fisheye lens, a headpano and a tripod. With these euipment, you can take good-quality fisheye photos which can be used to make 360 panoram. More information about the Recommended Equipment please refer to http://www.easypano.com/pw6-equipment.html. Then with panoweaver 6.00 professional and tourweaver 5.00 professioanl, you can make perfect virtual tour.

When you taking the series images, please keep the camera's settings is exact same, such as aperture, ISO, shutter speed, etc. I recommend you to use manual(M) Exposure mode to take images. Then these images will be with the same exposure and white balance.

When taking these images, there should be enough overlaps in each images, usually there should be least 15% overlap, or you will not be able to find enough match points in the images. Please take images at each 90 degree, and dont move the tripod when shooting these images.