First, buy a pack of fuses!
Fit a new fuse and test each item on the affected circuits one at a time, replacing the fuse each time it blows. That way you'll know exactly which circuit(s) have a fault.
Having identified what's causing the fault you'll then need to trace and check the wiring. Disconnect at the device end and test again, if fuse still blows then fault is with the wiring, if not then it's the device itself.
If the wiring has a connector at some point (most will go through at least one big multi-way plug) then disconnect there and test each side for a short to ground to narrow down the fault.
The only common place for wires to short is by rubbing on the frame of the radio behind the centre console, so I'd start there.