How do you remove Large Decals [advertising size] from my pickup?

Use a firm PLASTIC putty knife to carefully get the plastic itself off, then use something like GoofOff, or even alcohol, to remove the sticky residue.

WARNING: You may be left with a "negative" of the decals on your truck from sunfade - that is, from the general fading that you get from being exposed to the sun... but the part under the decal being a tad brighter.

... stay tuned, though, there may be others who will pipe in.

WD-40 will also help remove the sticky residue.

Hair drier. Warm it up first before scraping. Not too hot though. You will probably just end up peeling it off.

Hair drier. Warm it up first b4 scraping. Not too hot tho. You will probably just end up peeling it off.

Yes, that is correct, this is what decal manufacturers advise you to do. ;)

A steam cleaner or a hot water pressure washer with a 15 degree tip also.

This is what the larger truck firms use to take decals off the tractor trailers before they sell them