We spread my FIL's remains in a quiet, scenic spot that had had special meaning to FIL and MIL. It most likely wasn't entirely legal to do so (so I won't say specifically where it was), but it was quite a bit off the beaten path and it didn't take very long.
You can do it with as much or as little ceremony as suits you -- read a poem, say a prayer, just say a few words, whatever. Neither DH nor MIL are much for ceremony, so we just had a few moments of silence, and then went on our way.
I will add to what Gil mentioned, about the wind, something we didn't take into account -- and as DH started to scatter the ashes, from the box that they had been in, they blew right back toward him and ended up all over his sneakers. It was a little awkward to have to brush "Dad" off his shoes.
What we really wanted to do was scatter the remains at Giants Stadium, in East Rutherford, NJ, because both FIL and DH were/are lifelong, dedicated Giants football fans. (Ideally, DH would have liked to scatter them in the end zone). At the time we even knew someone with connections to the Giants, so we looked into it a little, but were told there was virtually no way we'd be able to do that -- and that we weren't the first people who'd ever wanted to do it, either.
"We reject as false the choice between our safety and our ideals. Our founding fathers, faced with perils we can scarcely imagine, drafted a charter to assure the rule of law and the rights of man, a charter expanded by the blood of generations. Those ideals still light the world, and we will not give them up for expedience's sake."
--President Barack Obama, 1/20/09