Deb- don't over-think it
As for sitting:
I'm a huge fan of sitting however I feel is necessary for the distance/terrian/effort that I'm doing! I don't think there's really a "right" or "wrong" way- usually, I'm back on the wide part of the saddle sitting square on my seat bones, but sometimes I'll roll forward, flatten my back a bit, and be supporting most of my weight on my ischium (click here for a pelvis bone diagram). Sometimes, I'm someplace in between! Just do whatever feels right for you.

As for saddles/fitting:
If you're getting soft tissue pain, chances are, you need a saddle with a cutout (or at least some sort of pressure-relief channel). Personally, whenever I've tried non-cutout saddles, not only do I get horribly sore/chafed soft tissue, the rest of my body (back, shoulders, hands, etc) hurts from trying to hold my pelvis in a position that keeps my soft tissue from getting squished! They'd always gave me the feeling that my fit was way off: I'd feel like the saddle was too far back, my bars were too low, and/or my stem was too short. However, as soon as I swapped for a cutout saddle, my bike fit felt fine (I actually ended up lowering my bars & going with a longer stem!).

I went through 16 saddles before I figured out what I like (I ride a Selle SMP Lite 209, which is still not perfect, but I can tolerate it). Based on my personal experience, I recommend the following saddle-searching steps:

1. Find out your seatbone width. Most shops have some sort of measuring device that you can use. Get a center-to-center measurement and look at saddles that are at least equal to or a little wider than that measurement.
2. Determine how much padding you want. Generally, less padding is going to result in a little seatbone soreness for the first few rides, but will give you fewer problems with saddle sores. A lot of padding can also close up your cutout once it starts to break down. Never a pleasant thing!
3. Shop around for your desired width/padding- ideally you'll find someplace that offers a satisfaction guarantee- Terry, specialized, bontrager, and some LBS's will allow you a certain time during which you can return a saddle if you don't like it. This can save you a lot of money! If you think that the SMP saddles look like something you'd like, check out cbike.com. They have a 10-day demo program.
4. Don't be put off by price or weight. Your comfort is more important than either of those things.
5. Once you get a saddle, get a basic re-fit (a lot of LBS's do this for free if you order through them). Because of differences in saddle and rail length/height, you often need to adjust the height and fore/aft position of a new saddle.
6. Ride! If your seatbones get sore, ride some more. If you start getting chafing/saddle sores, then it's likely that you and the saddle aren't meant to be! Return it (or sell it), and try again with a saddle that's got a different shape and/or padding.
7. Rinse and repeat until you find one that you love!