[Deciduous]

Stealing some dead person's identity just after they died is just asking to get caught and imprisoned for something, even if you didnt kill the person in question. The first poster also said it doesnt matter how you came across the body, but if someone just happened to drop dead from a heart attack in your kitchen, then obviously you wouldn't have to arse about with disposing of it.

It seems there are two main 'genres' of body disposal, excluding doing nothing. Either obscuring the body from view (probably easier but a greater likelihood of getting caught if someone finds it) or obliterating the body entirely so as to leave as litte evidence as possible.
Someone already mentioned putting it in roadworks, so it would be hidden for you, I was going to say in a building site.
I would opt for the second one, assuming I had just killed someone intentionally. Wrap it in plastic and, if you have a big enough freezer, chill it (if only to give you a little extra time to prepare and make cutting it up easier/less messy). I can't think of anything as accessible to everyone as burning the body, although it has the downside that you might attract attention.
Drive to the middle of nowhere, cut out a rectangle of topsoil big enough for the body, then dig out another 20cm or so. Dump the body in, syphon some petrol from the car and set fire to it all. Better put in everything you're wearing as well, remember to bring some clean clothes. If everything is cool we shouldn't even have any bones left (best bring a couple of old tyres to get the fire going good). Put the topsoil back on (grass and all) and tread it in, you might have a little excess to scatter about.
Hopefully it should look like nothing ever happened. Burn/scrap the car as soon as possible.
If you happen to work for a place that uses air curtain burners (for disposing of diseased cattle and the like) you could reduce a body to nothing in 5 minutes.

I'm sure there's holes in that somewhere, I'll have another think.