For raw conversion, working on a Vista PC with a recent dual-core processor and the maximum 4GB RAM, I'm still figuring out my own optimal approach. So far I haven't been happy with the results from ACR. As alternatives, I've been tinkering with C1 and Raw Therapee. I had some speed and stability issues with the RT 2.4 early release versions, but the RT 2.4 final version, just out, seems to have settled down nicely on my machine.
The C1 defaults are overcooked for my taste. And I'm still finding the user interface a bit awkward, which means that getting to a result I'm happy with takes more work than I'd prefer. For the moment, with RT 2.4 now stable, most of my effort is going into learning the ropes with that.
Re settings, that depends heavily on what you're trying to photograph and on your own preferences. FWIW, these are mine:
* Raw capture only.
* For general hand-held snapshooting with the 50/1.4 AF, I'm using single-shot, center-point AF. For manual focus with a variety of adapted 35mm M42 lenses, I've put in the M screen.
* ISO either 200 or 320, depending on the light. With the AF lens, I'm keeping the meter mode on aperture priority and the pattern on evaluative. It's running a bit hot for my taste, so I'll probably start dialing in -0.3 or -0.7 as a default. For the adapted M42 lenses, manual exposure only, a lot of seat-of-the-pants plus adjustment based on the histogram.
* For daylight snapshooting, AWB. For typical household tungsten lighting, I switch in the lowest value manual Kelvin setting. Since I'm fairly crazy about dynamic range, when my raw converter workflow settles down I'll probably experiment with UniWB.
* I've been switching on the anti-shake for speeds below 1/125, leaving it off otherwise. I've not yet tested this in a controlled way - this is just caution based on anecdotal reports from users of other cameras with AS, that at higher speeds it can sometimes make things worse. If I were working with longer lenses, or with something really heavy like the CZ 24-70, my threshold might be higher.
If you can tell us more about what you like to photograph and what kind of final output you're aiming for, perhaps folks here can give you more specific advice.