I write a little and have managed to get some things published here and there.
My advice is to get it all down on paper first, by which I mean, don't judge what you are writing, don't self criticize, just get it down.
Read lots of books. Especially similar to your chosen field/topic. Somehow, the more you read, the more you write.
Check your local Arts Center for Writing Groups/courses. Generally they are well run, and you get to meet some like minded people who can give you immediate feedback on your work.
A couple of Excellent Books... The Writers And Artists Yearbook 2006, published by A&C Black, London will answer many of your above questions (should be in local library) and The Artists Way by Julia Cameron, published by PAN, is a fountain of creative encouragement.
Best of luck with it!