Best tip I can give is to buy solder and flux from a reputable brand like Kester. You'll be doing a lot of soldering, so using good quality solder and flux will save you a lot of time, and also make it much easier to form good solid joints.
That and to make sure that you've tested RVLoader and all the relocations you intend to perform before trimming your Wii, and to make sure you trim a bit outside the guidelines to give yourself room to sand the board. Many a time have beginners trimmed on or just inside the lines and ended up severing essential traces and components.
Approach everything with caution and commonsense, don't cheap out on tools and parts, and ask all the questions you need. We're here to help!