Depth of field (what you want lots of) is dependent on 3 things:
1) the size of the aperture opening in the lens; commonly referred to as the f-stop. On video cameras the aperture is also called the iris.
2) the distance from the focal plane (in the camera) to the subject
3) the size of the focal plane (CCD or CMOS sensor on a digital still/video camera, or size of film stock on a film camera)
(DOF appears to be affected by the focal length of the lens, but that is an optical illusion. Visually however, it does have an affect because distances are compressed by longer lenses, so you may still want to consider it a factor)
regarding # 2, the further your subject (focus distance) is away, the more depth of field you will have.
regarding # 3, smaller focal planes yield more depth of field. e.g. a 1/4" CCD video camera has a lot more depth of field than a 1/2" CCD camera, which has a lot more depth of field than a 35mm (~1.4") film camera (or Red One).
What you are looking for is called "hyper focal distance", google that in quotes. The hyper focal distance of a lens is the focusing point at any aperture that yields maximum DOF. If you use hyper focal distance at f16 on a 35mm camera with a 50mm lens, the acceptable focus range will be from about 8ft to infinity. I've used this technique a lot shooting landscape photos.
You may want to also research "depth of field", also. Focus is relative, because only one plane is technically in sharpest focus at any one time. We measure DOF subjectively as the range that is close enough to being in focus that things appear sharp. It is still not a good substitute for critical focusing.
Having said all that, please try Google for more information. A lot has been written on this subject. However you will not find "the perfect lens", because it simply doesn't exist, except in CG. A lens with a very small aperture opening will give you great DOF, but you'll need to be shooting in bright sun to get enough light for your shot!