Ways to improve writing skills?

Okay I am hoping to come a novelist in my later youth, though after I am done with college I am hoping to come a Journalist for a magazine, making my way up from there. Though I have a very big problem when it comes to writing novels, I can not stay in one narrative form, I seem to jump from 1st person to 3rd person and I normally don't detect that I do it when I am proof reading. What I need is some simple techniques to help me stay in 1st person when I am writing, also pick it up when proof reading. Also if anyone knows any good websites to help improve writing skills, that test your knowledge can you please leave links :)