I use a mix of a straight Word document and behind-the-wheel. Very basic stuff.
My Word document has the character details (description, which may be detailed or 'looks like Harrison Ford', plus a bit of information about their background) and, as the novel develops, I add new things that the characters reveal about themselves that I hadn't realised at the start. It also has a basic chapter outline as events and developments move the story forward, and something has to happen in each chapter. I write the full chapter above that chapter's summary, so I remain on task and don't wander. If something happens that necessitates wandering off task, that's fine as sometimes it does happen - for instance, a minor character suddenly demands more attention in one scene, so I add them into some following chapter summaries so they don't flash and disappear.
My behind-the-wheel planning is the time in the car with the radio off, or on the tractor or on the mower, as I play out the next chapter in my mind - the conversations, the twists, the incensed, inflamed, or infuriated comments (the internal thesaurus gets a workout), the expressions on faces, the inner thoughts. It is virtually complete in my mind, so writing it down is easy.
There are novels in my head that are complete, and I'm fairly sure I could write them without any notes or planning as I've played them like movies for so long that I know how they go... but I'm not the writer others should emulate, so don't take notice of what I do. I'm hoping to be 'successful' but I'm taking the long way around. I have a middle grade series that only rarely has all four books under the 100k ranking. Then there are two big stand-alone genre-straddling books that don't follow the formula of successful indie writing, but they chug along OK, and some short stories plus a few little things that I published as a way of 'keeping them stored' (an advice book for teens and the stories I made up for my children when they were little - so I'm always surprised when any of these sell). So, please don't follow my example on anything, including planning. The same amount of effort and skill I've used so far, only on the successful formula (popular genre series - complete series, then another and another), combined with good marketing, should have an author earning 5k+ a month, not my very-lucky-if-I-make-1k-this-month, so do as I say, not as I do.