How much is too much for you? How little is too little? How do you find your happy medium? What must you describe about every character when you write?
I don't think I've mastered description yet. If anything I tend to do too much description, tossing it in all over the place - 'she shook her head, her brown curls falling into her face' or 'her blue eyes took in the forest scene with its lush green leaves and red and yellow wildflowers' type of thing. Possibly not quite to that extant though...
I always at some point include hair colour and general body type/size/height because I like to know what characters I read about are like, so I want to include information I look for in stories. That wouldn't be 'he's 6ft tall with short spiky black hair and a toned body' though, it's more likely to be dropping his hair colour in at one point and later mentioning his height compared to, say, a shelf he's reaching something off, or a small child who's talking to him.
Body type can be slotted in at any point - a woman not being able to make her hands meet while giving a friend a hug, or someone calling an insult to someone (stick insect or fatty, maybe) or describing the type of thing that person does for fun. Someone who spends all his time in fast food restaurants is likely to have a very different body type to someone who's a member of a running club.
What's the worst way to use and/or reveal character descriptions?
The worse way is when you get paragraphs of description with nothing to move the story forward at all. I try to avoid that! The second worse way is the 'looking in a mirror' technique, or the variation 'another character looking at him/her'.
How much of the scenery do you put into your novel and why?
I like to include scenery if it's relevant, but it not I just like to set the scene. If someone is in a train station you can have the noise of a train pulling interrupting a phone call and that's all you need to include, but if someone is meeting underneath a clock at the railway station you might want to add detail as the person searches for the clock - because in that instance, it might add to the tension as the person tries to find the clock in time.
Bonus: A picture is worth a thousand words... Draw us your main character!
I can't draw people very well, and I especially can't get people to turn out the way I imagine them in my head. I usually do internet searched to find a picture of someone who looks like how I imagine my main characters. This is the picture I found for Dawn Bell, the main character in my July Camp NaNoWriMo novel.