Hmmm... there's a bit to give, so I'm fighting on where to start...
OK- I'll start with style. Are you wanting to try for a manga style, realistic, or something like style? That'll determine if you want accurate proportions or not cause art isn't about photo accuracy, it's more about conveying a story. Style its a subset of marketing your art to me.
Nono- You're not crap. You look like you're starting out with art and that's perfectly normal. everyone starts somewhere ^^
OK, so a manga style huh? I can help less on manga styled art unfortunately, but it's all about dynamics and personality. A HUGE step forward for you would be to work on making your expressions. So far, they're very uncaring looking, but that's cause you don't know how an expression looks, right? Try having a mirror nearby to pull faces at. You'll get to recognise expression traits as you progress in art. http://pixhost.eu/avaxhome/avaxhome/2007-09-12/the_artist_complete_guide_to_facial_expression.jpg This book is my expressions bible. It's about an inch thick, but with manga styled, you don't need this levelled precision in expression cause it'll over crowd the face.
My second piece of advice is reference. Don't reference other manga art directly cause you don't learn, but reference a photo when you draw. The key with drawing a non realistic art style is that even though its stylised art, its still based off a real human figure. Because of this, you still need basic human proportions for it to look right (There are always exceptions- chibis for instance). Try finding a cool pose of a person on the net, and drawing it in your own style
Thirdly- you're still pretty new, so I wont go into composition, colour etc... but when you get confident, put your characters into a setting. Character drawings are fun to draw, but if you want something awesome, a location draws the viewer into the characters' story.
Lastly, and definitely not least, don't say your art is crap. Only *ever* compare your art to yourself. The harshest critique you should give you self is "I could draw better". When you can look at your art and say "I couldn't draw this picture any better at my current experience level." that, is when you grow as an artist :) And anyone can do it.
Give me a buzz if you have any questions ^^ Sorry that alot of it is very vague at the moment- alot of it is very trial and error. I think that once you get a push in the right direction though it'll get alot easier for you Never fear! *strikes a superman pose*