Okay, I won't say the 'P' word... but learning the basics, either from books (check your local library and/or bookstore) or by taking classes is a pretty good way to begin. Don't get frustrated if something doesn't turn out exactly the way you would like it to, but save that drawing to refer back to later -- sometimes, seeing that there HAS been improvement is a big boost to the confidence, and it shows up as even better output. Heck, save EVERYTHING you do -- get a portfolio and stuff it full, then get another, and another, and another... Don't limit yourself, either -- try to draw different things at different times of the day, different days of the week... Go look for some small object and try to draw it as it sits on a table; make it as true to life as you can... then draw it again, this time changing it to be what you imagine it looks like from the other side, without looking to see if you're right until you've finished. There are lots of things you can do, those are just a few suggestions to get you started.

I so understand the frustration of the picture not coming out onto the paper as you see it in your mind,but apparently this is normal!There is a book called ART AND FEAR which may help you(not a technique book)and DRAWING ON THE RIGHT SIDE OF THE BRAIN by BETTY EDWARDS which helps you train your brain to more accurately get things down on paper.If you see a photo of someone where there pose fits the picture in your head then use that photo for reference for your drawing,Deviant Art site has lots of Stock photo's of models in various poses which might help.Linda Ravenscroft's book might also help you.Good Luck with your quest!!!
Sarah :)