I'm well into the fuselage of my RV-3B, and I second Tony's advice to carefully study Randy's website. I also recommend studying the construction photos posted by several other RV-3 builders (including Tony). Randy's site has links to several construction photo logs, and others can be found in the archives of this forum.
Other general advice is not to assume that the plans are always correct, or that the parts you get from Van's will always match the plans. The biggest challenge is visualizing how adjacent (or nearby) parts interact, and how that interaction affects exact dimensions, rivet layout, and construction sequencing. Just expect that you will make a few mistakes and sometimes need to backtrack. If you have doubts about your results, ask a Technical Counselor for a second (or third) opinion. Don't be reluctant to re-make any parts that don't meet your standards!
Part of the fun of building a -3B (or any other non-pre-punched RV) is the mental challenge of figuring out how to make the parts and put them together efficiently and accurately. I have previously built both a pre-punched RV-10 and a non-pre-punch RV-6A. Though I love the -10 for its performance and capability, the -6A and the -3B are more interesting to build because of the concentration and creativity they require.
Good luck!
- Dan Benua
EAA Technical Counselor
RV Repeat Offender