The tracing paper is a good idea, but some people also use a gridding system to learn proportions and such. I wish I could give you a visual here, and I hope I don't jumble it up and make it confusing for you, but here are some tips I learned that help when drawing a person freehand. Assuming you're drawing a person straight-on from the front view, here's a rough idea of typical proportions:
Of course we all know the default guideline sketch of the head is most easily done as an upside-down egg. You can shift the lines later to fit what you're trying to do, this will just be a beginning guideline.
From there, draw a slightly curved line straight down the center from top to bottom. Then, divide that upside-down egg sideways into thirds. The two lines you draw for this should be curved a tad upwards, to help remind you of the shape of the face. The top line is a rough placement of the hairline, and the bottom is about where the center of the point of the nose should be.
From there, the eyes should be almost in the center between the hairline and the center line, but probably a bit closer to the center line. In figuring the size of the eyes and how far apart they should be, you should be able to fit one eye of the same size between them, and one on each side (of course you won't, but again, for referrence purpose).
The mouth should go about halfway between the center line and the chin. Usually, the ends of the mouth won't go past the pupils in the eyes.
Ears usually span from the eyebrow to the bottom of the nose (on the sides of course lol)
A body is usually 7 heads tall (including the head), arms usually never reach past mid-thigh (hands and fingers included, of course).
Most importantly though, sometimes we tend to think TOO MUCH about what we're doing. Daydream a little when you're drawing . Think about the drawing and what you're doing, and concentrate on it of course, but don't stress over it too much. And, remember that even when you're really good at something one way, learning any new thing takes time and trial and error. Maybe you're just so used to drawing with a reference that you psych yourself out when you don't have a ref. You'll get it

Good luck and I hope I made SOME sense here!
