I mostly write poetry, but I have written/am writing 2 novels. I've discovered I can't write short stories. Not sure why, they just never work. I've never really tried much else except journal/diary and blog writing.
I have another novel idea percolating, but it's still nowhere solid enough for me to really start working on it, but I do write about it occasionally. I have two writing journals: one where I write whatever I'm working on and one where I write about my writing.
This second journal is all about my novels and contains ideas, sketches of plotlines, information about characters, details about their past. I also ask questions and remind myself to expand and write about certain things. Often I just journal about what I'm currently doing. I have misplaced the one I used for my first novel and my first draft of my second and I miss it terribly. It was the chronicles of writing those first novels: raw, hopeful and frustrated. I hope it's stashed in the loft in Scotland as I hate losing writing.
Fiction and poetry writing are very different processes for me. When I was working on the first novel I got a SAC grant to write it and it was almost like a full time job, I wrote every morning for hours, then had lunch and went to the allotment and spent a few hours there, sometimes writing if the weather was poor and then I'd come home and type up what I wrote and did some rereading and editing. Then it'd be time to make dinner. I did this for a month, I think and I really enjoyed it, but it was hard work. Editing and rewriting the first draft was even harder. I need longer blocks, much more time and commitment for fiction.
Poetry I can do in small parcels of time. I rarely sit and write a whole poem or finish one in a day or even a few days. I write a line or two here, go and edit another poem that's still in progress. I do some free writing around the subject and then pick out the good phrases that could be used as the backbone of a new poem. Poems take months, sometimes years to feel solid. And then I still reexamine and edit them a bit before I submit them for publication.
Rewriting and editing happens as I write poetry, I'm always tinkering with lines, where I usually leave big edits in fiction until I've finished the complete project.
Two books I'd recommend for getting started with writing is Natalie Goldberg's Writing Down the Bones and John Gardener's The Art of Fiction. They are very different in style, but both equally useful in their own way.
Goldberg's is more to do with starting from scratch and getting into the habit of writing. It's good if you're a beginner or if you have a project you're starting. It's less about technique but more about state of mind and getting your bum of the seat. She's more 'spiritual' about writing, but is still all about doing the work.
Gardener's book is more about craft: technical and more academic. It starts with an essay and then moves to common problems and techniques. It also has a section on plotting which I found invaluable as it's not my strong point.
You have to be wary about buying and reading books about learning to write. I don't believe anyone can teach you, but they often can give you inspiration, direction and assistance. But it's easy to spend a lot of time (and money) buying and reading these books rather than writing.
I prefer the more practical books that have lots of exercises or writing prompts. My favourite for myself and for when I was teaching creative writing was A Writer's Book of Days by Judy Reeves. It had a hundreds of prompts that worked for poetry and fiction and could be used to just get into the habit of writing but to also work on a piece already started.
I've actually just put it in my basket for my next book order as my copy has been in Scotland for 7 years and it has now been revised so a new copy is definitely needed to help me get back into the swing of things.