Somebody, somewhere, put writers into two different categories: Those who write by just letting the characters go on the page, and those who plan things out. They are known as Pantsers (by the seat of their pants) and Outliners.
Now, if you're a Pantser, here's the goal: You're going to write a crappy first draft. You will go down roads, end up at dead ends, try to write yourself out of boxes, and find your characters go in strange, unusual and interesting places. You will be writing anarchy. You will find gold nuggets in those crappy first drafts.
If you're an Outliner, you plan things out. Either a quick rough draft or a detailed plan with "beats" and scenes. The goal there: You plan things out so when you write, you have a guide of where your characters are going.
Pantsers are improv. Outliners are directors.
What's wrong with combining the two? Here's an example.
First, I get an idea: Drake, a dragon in human form, is exploring his sexuality.
Then, to get all mystical on you, I then toss it to my muses. I have two of them. One is Calliope, who is into the actual writing. She's the one who comes up with the dialogue, the scene in my head, and lets the characters go to town. The other is Electra. I know she's not a real muse. She's based a little bit on Frank Miller's Electra: Assassin. She's the violent one, the one who can write about blood and gore and glory of battle. Calliope can too, describing the fighting scenes for me, but when it comes to what happens during the battle, how things get hurt, that's Electra's domain.
Going back to the story: Drake goes to a seedy part of town. What happens there?
Now, at this point, I could just let the characters run riot. But I know the end.
Drake realizes that he prefers some emotion with his sex.
That's my outline. The beginning and the end.
I have a couple of things in mind that I'm going to bring up:
Drake meets a couple of prostitutes and finds one he likes, then goes and has sex with him/her (not sure yet who) and s/he does something that shocks Drake into realizing this was only sex, and he finds he doesn't like that.
Now usually, this is all in my head. I don't like writing it out because it sounds like a real, honest to God outline, and heaven forbid I do that! Calliope hates "detailed" outlines.
There's nothing wrong with pantsing, just realize that you're going to end up with a lot of crap. However if you have some sort of plan, that will make things easier. That does not mean bullet-points, a detailed synopsis, full scenes written out. The planning section might make your muse chomp at the bit or piss her off because you're not getting into the down-and-dirty.
Know thy muse, and what she (or he!) likes and work with her. Don't flog her or she'll get pissed.