Remote Research lays out a comprehensive framework for starting to conduct research studies at your company, and is useful for beginners or for filling in the gaps in your mental model. However it seems more targeted towards large companies with established UX practices than towards startups. If you are executing alone—perhaps as a one-man UX team—you may still feel a gap between theory and execution.
I finished reading Web Form Design recently on the recommendation of a mentor. The author makes a good case about web forms being a high leverage area to invest design efforts. The combination of forms being mandatory, complex, and not particularly sexy, results in an experience that is often the worst part of a user’s interaction with your product. He then breaks down the form into the building blocks of Labels, Input Fields, and Actions, then lays out best practices for each. Here are a few snippets from the book that resonated with me.