For the deck, my technique:

Yes, for a "generic" installation you frame it, then use CDX ply on the top of the frame, then 15 lb felt on top of the ply, then use thinset and screws to set the cement board on top of the ply/felt.

If you think you'll be getting a lot of water/splashing on the tub deck, you can treat the top surface of the cement board instead of using felt underneath the cement board. Use RedGard, Kerdi, or some other topical waterproofing to better protect the deck. You can also run the waterproofing up the walls a little bit.

Here's where paths can diverge regarding tub installation.

After the cement board is installed, some will install the tub and leave it shimmed high so that the deck tiles can be slipped under the tub's rim when the tiling is done at a later date. Others will tile the deck first, then drop the tub in on top of the tile. Some others even drop the tub in with the rim in contact with the cement board, then tile up to the edge of the tub rim, and caulk the gap.

I prefer tiling the deck completely then dropping the tub in on top of the tile.

You only put the mortar bed down at the moment when you are ready to set the tub. And remember, it's the base of the tub (mortar bed) that supports the tub, not the rim. You don't want the tub "hanging" from the rim. The mortar bed (or tub feet for a non-mortared installation) should support the tub with the rim just contacting the tile.

After the tub is set you can make the plumbing connections, test for leaks, then tile the front apron.

For a soaking tub there's generally no need to treat the adjacent walls unless you think your soaks will create the occasional tidal wave. If you're going to add a baseboard or trim piece where the tub deck meets the wall, you can fold the tar paper (or previously mentioned Kerdi or Redgard) up the wall a few inches and cover it with the trim piece. Some people also run a row of tile on the wall as a transition.

Caulk the junction where the tub deck meets the wall trim or wall tile.

There should be no need to remove and replace the existing wall board around a soaking tub installation.

I do all the work myself, so I can control the work order and shift from one thing to another. If you're subbing out the tile, you might be better served by arranging things so your tiler can tile everything at once to minimize site visits and installation costs. In that case an access panel for the plumbing would help.

Thanks, Mongo, that's great. I will have some Kerdi left over from our shower, so I can use that.

So on the top, it's this order: Frame, ply, thinset, kerdi, thinset, cement board, thinset, tile?

I'm planning to tile several rows up along the walls as a design choice (as a continuation of the tile backsplash behind the adjacent vanity) so I will just put Kerdi behind the tile.

For the tub deck: frame, then ply on top of the framing, then thinset & cement board on top of the ply, then thinset & Kerdi on top of the cement board, then thinset & tile on the Kerdi.

Having the Kerdi on top of your cement board will prevent the cement board from wetting.

For the tub apron, it's not a "wet" area so you can do cement board right over the vertical framing and tile right on the cement board.

I picked up a nice tip somewhere:

when ready to set the tub into the mortar bed, have the drain hook-up ready too and fill the tub with water so it sets evenly into the mortar bed. We were retards with our first tub (too embarrassed to describe in detail), and this was perfect when we set the master tub!

Thanks for the replies!

One more thing: the drywall behind the tub where I will tile has places where the top layer is peeled off (where the old tub surround was glued to the wall). I plan to skim coat those areas to make sure the wall is fairly smooth. Also, some of the wallboard has a light orange peel texture with semi-gloss paint. Will that affect the kerdi?

Darn it, sorry. I just looked at the manufacturer's instructions and have a couple more questions:

I plan to attach the frame to the wall studs using long wood screws - will that suffice? Do I also need to use vertical or horizontal support boards since the edge of the tub is resting on the top of the tub deck?

You don't want the deck flexing away from the tub, so yes, I always add cripple studs or "legs" to support the frame of the tub deck, even where it's screwed into a wall. And where it's screwed into a wall make sure you catch a wall stud. But don;t hit any plumbing lines!

Use wood screws, standard deck screws from the box stores are fine. No drywall screws.

For the semi-gloss painted drywall, you can scuff sand a bit with coarse grit sandpaper to roughen the paint up a bit, then thinset the Kerdi to it.

Any divots in the drywall surface will get filled with thinset when you cover it with Kerdi.

Divots in the drywall where you will paint can be filled with joint compound or spackle.