A - Our design process starts with a discussion of feature ideas and requirements from the code side. Then work goes in parallel until each team has a workable mockup/prototype. This period of work alone is critical to the development of the app from the visual and user experience side of things. It also gives me freedom to try lots of new ideas. I'll usually do a couple of revisions based on comments from my co-founders, and then get some outside opinions.
B - I fear that user interface and usability comes more from trial and error than reading. I haven't found a good resource for the technical side of design, but olalonde's link to uxmovement.com looks great.
C - Our startup has 2 coders and 1 designer. We're a rails shop, and I know enough ruby to implement my designs. This mix usually works really well as far as delegation of work. I'm not sure how standard this is.
D - Can't say much here since I started on the design side and have more recently been programming.
As an aside - if you're comfortable in css and are adding a new page or feature to an existing site, I've found that it can be fast to prototype in html rather than Photoshop/Illustrator.