What should be the ratio of the fuselage and wings in a maximum dimension limited condition supersonic delta wing aircraft? Also can anybody explain clearly the "supersonic area rule" or "Whitcomb area rule"? Is there anything else I need to take care of while designing a fuselage for supersonic conditions? Thanks.
There is no ideal ratio. Make the wing as big as it needs to be for your take-off run, your cruising altitude or your approach speed, whatever demands the biggest wing, and make the fuselage just big enough to hold the pilot(s) and all equipment, payload, fuel and whatever you choose to carry around. Asking for a specific ratio without any details on the mission or the design parameters is silly.
The comments tell me I should say something about area ruling, though. Terry correctly mentions the x-wise gradient of the aircraft's cross section, but this is only helpful at Mach 1. At higher speeds, you need to look at the area which is covered by Mach cones which run along the longitudinal axis. Sum up the area of the intersection between those Mach cones and your aircraft's structure, and make the lengthwise distribution follow a Sears-Haack-body. Please note that the inclination of those Mach cones varies with angle of attack, so there is not a single optimum shape, but only a best compromise for all expected flight conditions.
Area ruling is only helpful around Mach 1, but there (or slightly above) is the transsonic drag maximum, and area ruling helps to get across this quickly, even with the high thrust of modern engines. If your task is to get to this strange radar blip at 16 km altitude in a hurry, every second counts. Also, modern airliners need to employ area ruling techniques to make cruise Mach numbers above Mach 0.8 economical.
And this is just scratching the surface ...