Alright guys I've always wanted to write some kind of book/story because I'm creative, however despite doing English Language at A-Levels at school I was never really good and there's a lot of flaws in my grammar etc So I want to get the fundamentals down before I go into writing something because I'd be wasting my time. What's the best step to take? Cheers
READ! read constantly!! read and study the best writings of the best writers, to 'absorb' how it's done, how it looks/sounds/feels... you can't learn to write well if you don't read well and continually...
This really is the best advice you can get, but I'd supplement it with some other things too. Check out Stephen King's On Writing and Orson Scott Card's Elements of Fiction Writing, both great references. Once you get things out of your mind and onto the paper, the grammar can be ironed out, or, though I personally dislike it, you could be like Hubert Selby, Jr. and just ignore the rules of grammar and punctuation. Some people feel it adds to the "artistic value" of the work. I, however, think that's stupid. But he's a famous writer and I'm not, so take that as you will.
I'd say that it's through reading _and_ writing that you really become aware of good and bad ways to write. So I'd suggest that you write, even if you don't feel ready yet. You don't need to write a novel or anything formal - you could write a blog, or a journal, or almost anything that makes you comfortable with producing sentences and paragraphs.