Go to radio shack and get the 6' ADAPTAPLUG extension cord and the "F" ADAPTAPLUG. Total cost should be like $6. All you have to do is cut the male end off the extension and connect the wire with the white stripe to ground and the black wire to switched 12V. I use the gauge fuse (purple 3A) , because A) it's only on in the RUN, not ACC position, so I can have the radio on without the detector beeping, and B) detectors only draw like 1/4 to 1/2A , and you don't want that tiny wire on a high amp fuse. If the wire gets pinched and shorts out, it'll heat up and burn the insulation off almost instantly so you want it to blow very fast. You can get piggyback fuse taps to tap right into the fuse block, or if you can, find the gauge cluster feed coming out of the block and use a Scotchlock or spade tap.
Then route the wire under your moulding to the desired location (mine is above the rearview mirror) and plug the Adaptaplug into the female end. They can plug in 2 ways - make sure it's set up to TIP POSITIVE or you'll burn out the detector.
Matt {peace}