As a total pantser I don't feel that I have tips for you. Advice? I could probably come up with some. Mainly, be true to yourself and what you want to say and ultimately, how you want to say it.
As to planning? I get an idea sometimes for a story or a character or even just a title and I let it grow from there.
I operate of the principle of "knowing." I know who my characters are, basically. I learn more about them as I write, but I know who they are at their core. I know what kind of story it is in many ways such as will it be long, will it be a mystery, will it be a little scary, etc. As the majority of stories contain some sort of mystery element to it (a lot of Harry Potter does) there's always a touch of that.
I'll get an idea for a line or a scene and I usually will write it down so that I don't forget it... notoriously bad for forgetting the brilliant ideas in the showers.
I'm kind of like a Nike's ad (or is that addidas?). I just do it.
I never get stuck or have writer's block. Correction, I haven't experienced it yet, that doesn't mean it won't happen later. If I do have some doubts I usually have enough stories started and are in different stages that I simply shift gears and step into one of them. Having multiple stories started and in various degrees of completion is because I'm a bit of a "ooh, that's shiney" type person who can get distracted.
I think visually so if I have a character walking down a street I know which door he's going to knock on and I know who the character is that will open it, I know what season it is, if the buildings are brick or wood, if birds are about, if there's a factory nearby, what color the character is wearing. I don't know how I know those things, I just do. Maybe it's because I've done some acting and some improve and you have to be able to do that quickly sometimes.
As far as the story... I'm only along for the ride to see what happens next. Sometimes I think I know how I want it to end but... maybe the characters or the location has a different opinion on that.
Write hard, write true