Creative Writing discussion

I am about to start my fourth novel, but it's my first time taking a crack at one since high school.

In the past, I have always just started writing with a vague idea of where the plot was headed - and I think that's because my past novels were so character driven. Now I have a much more elaborate idea in my head (no longer the high school girl-meets-girl type of book), but I don't know where to start.

Or should I say, when to start.

Writers: do you start with a vague idea and run with it? Or do you plan everything out? I need help.

I do both haha
but I have found that depending on how invested you are in the idea, it can fall short without some form of plan. I don't, now, usually plan anything past five chapters in the case that I scrap the idea, but make sure I have the full idea saved.
plus my stories tend to veer away from the planning I do, so that's part of the five chapter thing

I get an idea- or a whole thing of two people talking in my head and then go with it. I just start writing. There is no planing things out with me.

@sucre'd fiend - I think I need an approach somewhere less specific than your route but more specific than @Cassie

hmm...