First of all you need a single laser that you divide into two beams (to produce a hologram you need coherent light) this ca be done with a semi-transparant mirror.
To spread the light you diffract it through a tiny hole (a pinhole for us photogs) and you do that with both beams. The placement of the pinholes depends on the area that you need to cover with light.
In order to produce an image you let one diffracted beam reflect of the object and then onto the plate while the other diffracted beam goes directly to the plate. The diffraction image on the plate can now be used to reproduce the light coming from any of the light sources when hit by light from the other. Hitting the plate with the laser beam that didn't reflect on the object will create the image of the object (and the other way around if you ever mange that setup).
The problem with holograms and photographic material is that they are not consistent enough to to used. The plastic base is not solid not to mention that the emulsion moves with humidity (remember that a shift of half the wavelength will, cancel the image). For this reason holograms are not made on photographic emulsions but special emulsions on glass plates (and they still shift a little in colour).
The kind of holograms that you see on credit cards etc are pressed and not recorded and that is another story (still they need a stable base so they are done on metal)