Ah, another wiki user. I'm curious, what wiki program do you use?
For my process, I tend to start out with a rough outline in a word document. That outline will get split into acts, and then into an outline of all major events as I write. Lately, for larger works, I tend to gravitate towards a wiki (I use Zim) to organize the finer details of characters and worldbuilding. It really helps to keep track of all the little details, all of the minor plot threads, and the complexities of characters. I've found that kind of organized information especially helpful during the editing and polishing process.
As for the broader question: what to focus on when you start out. If I had to condense the how-to-plan part of writing into a singular piece of advice, then it would be this: everything has a beginning, middle, and end. Know where your plot starts, know where it ends, and have a rough idea of how to get from point A to B. The same applies to the protagonist. Know where they start out and how their personality develops throughout the novel.
Nothing has helped my own writing more than getting this basic principle down. For me, it meant the difference between seeing a story through to the end, and abandoning it halfway through because I had no idea where I was going with it.