Toilets, Sinks, Showers, Tubs and Disposals - New Tub Install

I bought a house and am in middle of fixing it up before I move in. The main part I'm working on is the bathroom. It's down to the studs on the wall and just slats on top of the joists on the floor. My plan is to put in a new tub, toilet, and pedestal sink. I allready got the new faucet up and raised the shower head it was way to low for me. Now I need to install the tub (it's a steel tub). Someone told me that I should put cement board under the tub along with the whole bathroom (I'm putting in ceramic tile on the floor). Is this something that is recomened or should i just put the tub on the slats. I was going to put up green board around the tub, but from what I have read online you shouldn't use greenboard instead use cement board. Is this correct and how hard is it working with the cement board. Also I've heard people say that they put down a glob of thin-set under the tub for extra support, is this something I should do with a steel tub (only heard it mentioned with acrylic tubs) and if so how do i go about this so it won't ooze out of the space between the slats on the floor (If I shouldn't put down cement board under the tub)

Thanks

First off I would overlay the entire floor with OSB or Plywood. Then I'd notch the studs where the edge of the tub will rest so when you install the wallboard it will sit flat.
Then I would install the tub on a blob of thinset covered with plastic -- so what if it oozes out, clean it up.
Then install 4-6 mil vinyl on the wall for a vapor barrier and install cement board on top of that.
Then I'd install 1/4" cement board all over the floor set in thinset and screwed down. There is no need for cement board under the tub.
Then tile.

Thanks for your reply and help.

After looking online at cement board I have another couple of questions. I'm putting a tub surround up but i am wondering about the rest of the wall. From what I've seen cement board is real ruff on the outer surface and I want to pant above the surround. Also am I correct in assuming I can use dens armor plus for the rest of the bathroom, and just use the cement board for around the tub. If I can use dens armor plus for the rest of the bathroom could I also use it above the surround, and possible just slightly below it?

Thanks