Completely New to Orchids and Need Help

[A_in_Houston]

This is going to be long.
My boss will purchase blooming orchids, and then pass them on when they finish blooming. I tried one or two in the past, but failed dismally with them. I don't want that to happen again.

I was given six orchids today. I doubt that they are potted correctly and I'm unsure of their conditions. They probably all finished flowering within the past couple of months. I need someone to tell me what to do.

Three have no tags, and I don't know their names, but they have the common large, thick, over-sized egg-shaped leaves (these are the kind I tried previously). They're in beat-up clear plastic pots with sphagnum moss and styrofoam at the bottom. They seem rather wet, but it could be they were just watered.

The other three have tags with basic care instructions that are all about the same:
Odontoglossum/Oncidium intergeneric
Epidendrum
D. aggregatum

The Odontoglossum/Oncidium intergeneric is in a green plastic pot with an indented bottom designed to drain well, but its damp enough that the top bark has green growing on it. The potting material is small bark, and there are little white roots on the surface, but I can't get the plant out of the pot right now in order to see how the rest of it looks. The leaves are a bit pale in places, mainly towards the base.

The Epidendrum is similiarly potted with maybe a bit of moss mixed in, a little more damp. There are white, flat (squashed) roots sticking out the drainage slits. Its been severely cut back and the leaves are pale, like they may fall off, and have a touch of rust color on some of them.

The D. aggregatum has also been cut back in places. Its sitting on large bark. The roots are crackly dry (but not breaking when handled) and white and the whole thing lifts easily out of the pot, leaving the bark behind. There are a fair number of new 'barrels' with single leaves on top. The older 'barrels' have support spines sticking out, and I'm wondering if they swell to hold water. It looks healthy up top, but I'm concerned about the roots. It seems too dry.

So, what do I need to do?

Since I'm in Houston, I'm planning on keeping them indoors (previous failures were outdoors, different house). I now have a room with a large SE window where the room as a whole gets a lot of good, filtered light during the day. The other option is a West facing window on the side of the house, so it has limited sun exposure except at the height of the day since the neighbor's house is nearby. Which would be best?

Is Houston's humidity high enough?
Do I just need to water occasionally?
Which need repotted?
Do these all get treated pretty much the same, or is there something special about them?
What do I feed them with?
When can I expect them to bloom again?
I've heard of dormancy, but I don't know which need it, if its something I have to cause to happen or if it just happens, what the conditions are for it, how long it should last, or how to bring the plant out of it.

Thanks for reading, and thanks for your assistance.

Amy, in Houston