I often see comments by writers in blogs and magazines who claim that almost every time they tell someone what they do for a living they get the response 'I'd love to write a book'. They then go on to reflect on why these people don't do just that so I thought I'd put forward my own ideas. To me it's very simple. Writing is BLOODY HARD WORK.
O.k. maybe it's not too difficult to think up a scenario and vague plot. But when you get down to the details of the story, characterisation, dialogue etc. it takes a lot of effort. I don't know about you but I sometimes agonise for ages over single sentences, even words. I sweat and I get headaches. Then there's spelling, grammar...
And the hardest part? Sorry to bring up a sporting analogy yet again but I used to have my own ideas about that too. I used to compete at triathlon. The races were what I looked forward to but the training took a lot of self discipline. And it didn't matter how cold that lake was or how muddy the the run course or how steep those hills were that you felt if you went any slower you might as well get off your bike and walk. Nothing compared with taking that first step out of the front door and forcing yourself to go out training. It could be a freezing January night or a hot summer afternoon when everyone else is outside drinking beer. Just to strap on your trainers and drag yourself from in front of the TV and go out and do the work - that's what took the effort.
So it is with writing. The first words are the hardest to come up with. So my advice would be to take that first step. Get a scrap of paper, a fag packet, a bus ticket, anything. Write a sentence and that's it. You're a writer.