Newbie needing to improve

[Mez]

Hey all,
I'm new here but not to drawing. I've been interested all 14 years of my life. I seem to always have a pencil in my hand. Recently I've been getting into it more, doing 'daily drawings' if you like.
I was always told that I had a natural talent which I believed... until I came here! Some work I've seen on this forum is truly amazing.
The reason I'm here is to improve my drawing skill, which I seem to be struggling with. If anyone has any advice, please feel free. :^^:
Anyhoo, here are my drawings from the past week or two. Some of you may recognise these people.

Good Charlotte:
Joel Madden:
http://img.photobucket.com/albums/v721/TheRealMez/Drawings/Joel001.jpg
Benji Madden:
http://img.photobucket.com/albums/v721/TheRealMez/Drawings/Picture.jpg
Billy Martin:
http://img.photobucket.com/albums/v721/TheRealMez/Drawings/Billy001.jpg
Paul Thomas:
http://img.photobucket.com/albums/v721/TheRealMez/Drawings/WasmeanttobePaulThomas.jpg

Green Day:
Billie Joe Armstrong:
http://img.photobucket.com/albums/v721/TheRealMez/Drawings/BillieJoe.jpg
http://img.photobucket.com/albums/v721/TheRealMez/Drawings/BillieJoesilhouette.jpg
http://img.photobucket.com/albums/v721/TheRealMez/Drawings/BillieJoesketch.jpg
All:
http://img.photobucket.com/albums/v721/TheRealMez/Drawings/GreenDayEuphoriacover.jpg

Various others:
Dragon:
http://img.photobucket.com/albums/v721/TheRealMez/Drawings/dragon.jpg
Crocodile *unfinished*:
http://img.photobucket.com/albums/v721/TheRealMez/Drawings/crocunfinished.jpg

Sorry there are so many. :S