I suppose there's always a few tools of the trade that a writer needs to get by. There are a couple of obvious ones, which I'll go into shortly, but there are also more complex tools that people don't quite understand are theirs for the use.
To begin - you can't write, physically write, without either (a) a pen and paper or (b) a computer of some sort. One or the other will do, but you can use both. Now, the paper is best with lines, to make sure you write in a uniform way (i.e. so you don't write at a slant...), unless you're doing a comic of some description, in which case blank paper is best. Pens should be black or blue, or at the very least a dark colour. You need to be able to read what you write. As for the computer - you don't need the most up to date software on it, and in fact you can use a typewriter instead, but you just need to be able to save it, change it, and, preferably, be able to format it. Formatting it easy - most publishers request double-line spacing, to make it easier to read. If you don't plan on submitting, however, you don't even need to worry about it!
As for those complex tools... the pen and paper and computer are all useless without these. The first one is your imagination. Too obvious? It's a tool you can't refill like a pen, you can't just switch on like a computer, or load with paper. Your imagination can wear thin, and it's important to remember that it's okay. Most people call this "writers block", and it's possible to beat it with a number of different techniques.
Over the years, I've gathered a few of these techniques. One recommendation is to try a new type of music - it can stimulate your brain in a different way. You might listen to a rap artist for the first time, ever, and realise that your story is somewhat lacking in the problems of every day life. You might realise that maybe your London based novel doesn't need to be a peaceful story of boy-meets-girl, but can be a story of boy-meets-girl-but-is-in-a-gang-war-with-her. Okay, that's a little over the top, but it's true to life in that these events can happen, and that you're not following the same pattern as everyone else. Although, if you're using that idea, I might recommend reading Romeo and Juliet first so you know exactly what not to write - that story has been told over and over again, and a gang-twist isn't original for it (the movie adaptation of Romeo and Juliet is proof of this.) But my point still lies - you can take an idea you get from a song, any song, and use to change your story.
You can also go for a walk - fresh air does the brain good, and if you take a different route than you usually do, your imagination will thank you for it later. You can even use the little coincidences of your walk as the formation of a story. I did it before, where all the characters, nameless if I remember, were based on the actual people who I'd seen or interacted with on my way to choir.
Listen to conversations on the bus. You might find that you can make a story out of two people talking to one another. Or, if someone's on their phone, you have the basis of a conversation you can fill in to suit your story. And, while we're discussing phones, did you ever notice how people like to play music through their phones at the back of the bus? Just saying... (there's a story in there too)
Other options that will help your imaginarium come to life again are to look at the pre-existing ideas already available to you - look at some television, watch a movie, read a book. Or look at your own stuff, old, discarded ideas, and shift the context of the events around to suit your current Work In Progress.
Following up your imagination, you've got your experiences. I've touched lightly on this with my cures for Out Of Imagination, but I feel it could do with some more work. However old you are, nineteen or ninety, you have experiences at your disposal. If you think, "I'm too young," think again.
I'm nineteen years old. I've been bullied, friendless and depressed. And yet, I've also made some of the best friends in the world, started an anti-bullying campaign, been happy for weeks at a time (and it usually takes something really to bring me down again). I've been to Barcelona twice, and it was a different city both times. I've been to Portugal once, Menorca once, Lanzarote about seven times, and every time we did something different, or did things very much the same and felt different emotions each time. I've been in a Mini-Company in transition year, ran a Young Social Innovators project, had a job in a bookshop for two and a half years, sung in my primary school choir for four years and my friend Niamh's choir for two and half, been to three institutes of education (primary school, secondary school and, now, college) and I've made new friends at each one. I've joined a number of social networking sites, and with the exception of Facebook, I've made great new friends on each one. And I've lost three grandparents, seen my great-grandmother go through dementia, felt my heart ripped out by a girl. But I've found happiness in a number of great television shows, I see a new movie almost every week, and I've read more stories than I can even remember. All that, and I haven't even mentioned the writing, which in itself gave me a new outlook on life, a hobby, friends in the writers group I set up and something to talk about every time it happens to come up in conversation.
And I'm only nineteen! That's not even a complete list of the things I've done, and yet there's so much to take from. A lot of that I did by the time I was sixteen! You have no excuses, only experiences. You just need to start thinking about your life and you'll realise that you've done things. They might not stick out at first - you might think you've had the same job for ten years, had the same friends, and done the same thing every single night, and been with the same man or woman for all that time and say, "That's not an experience." But I tell you this, everything is an experience, and every experience is something you can write about. Remember, context in your experiences is everything!
You've got your voice to go along with all of this. Now, this might seem a bit strange, but a lot of writers don't write the way they talk. They make their language more posh and try to be someone they're not. You don't have to do that too. You can write the way you want to write, because at the end of the day, it's your writing that you should be concerned with. Roddy Doyle, for example, wrote an entire novel in colloquialisms and look where he is! Use your own voice, or at least establish one for yourself that you're comfortable with. Don't try to write like everyone else if that's not what you want to do.
Now, you'll have to excuse me - ironically enough, while writing this I lost my train of thought and can't write any more. Go figure. But I think what I have here should help any writer out there understand what they have. Remember - you have your physical tools, but you also have you imagination, your experiences, your voice, and, and these are things I don't have time for detail, you have your own decisions for the story, and you know the characters. Believe it or not, even those fictional beings you made up can help you craft your tale.
Writer, I wish you good luck.