@Denver Bill went to AutoZone and got their LED strips (immediate satisfaction). The way to get them to stay pretty much forever is:
Wash the area with car soap, then rinse it thoroughly.
Test fit the light placement. Get some zip-ties, small clamps, string, something to hold the lights in place and test the everything out before gluing them. Tape off the start and end points, and use masking tape with notes to document problem areas.
Electrical wiring should be temporary, not only to see how it looks but to test that everything works as expected. I suggest adding a fuse if you're tying them into a circuit such as the headlights. (LEDs -> small fuse -> headlight power)
Use 90% polypropyl alcohol and paper towel / microfiber cloth to clean the area until the paper towel / cloth has no dirt.
Use two coats of 3M Primer 94. Coat one side, wait five minutes, coat the same side again, wait five minutes. Do not coat the other side, putting the lights on takes too long. You can do wiring meanwhile.
Peel a little of the backing sheet off the lights and start the LED strip installation. Work a few inches at a time, using your clean fingers as guides. Press into place, it'll stay.
Where the LEDs made a bend around a corner they will bow out, leaving an opening. Fill it with clear adhesive.