I've been trying to write for a very long time, and I'm brimming with so many diffrent ideas, in diffrent gneres. For example I have ideas for a teenage fantasy romance, I also have ideas for an adult romance and an adult crime thriller. I'm just full of so many diffrent ideas, I always writer my ideas down and I always intend to write a novel about each and every one. However... although I have all these fantastic ideas, I find it so diffuclt to actually write it. I never get anything finished, not even the first chapter, I end up doodling all over my work and writer 'Argh, I can't do it' HELP!
It sounds as if you need plot bunny daycare. (See the Nanowrimo forums here http://www.nanowrimo.org/en/forums/nanowrimo-ate-my-soul/threads/965 ) During Nanowrimo everyone drops off the plot bunnies disturbing them from the actual story they are trying to write. Oh, and beware of Alphonse. Although I believe they did triple reinforce his cage last year. He took a bite out of most of the other bunnies in 2009.
Joking aside, Nanowrimo might be the answer. Although their encouragement is to produce words at a phenomenal rate regardless of quality, it certainly teaches you to focus to task. I did it in 2009 and if I had the right project in mind would definitely do it again. The support you get from everyone online in the month of November is just amazing. People all around the world take part. I was on an island in the atlantic at the time and was finding support from ex-pats in Spain and the south of France, but also from my home city group. The writing exercises and suggestions fire you on and some city groups even meet to write together on some nights of the month. There is no better encouragement anywhere for seeing an idea through to the bitter end. It might not produce the best novel you have in you, but once you've done it once...
Lots of useful tips here.
Here is another tip from the famous author Graham Greene. Write 300 words a day. It does not sound much, but it is 2,100 words a week, which equates to 109.200 a year.
This follows on from Jennifer's excellent advice.
This is how I did it.
I don't know what type of story you write but lets say it's a novel around 70k words (mine was HF so I had 90-100k to write). If you take 3k words as a reasonable chapter length you'll need 23, so write a list; 1-23. Then write an idea alongside each number. You might find you can write 3k words on one idea, but if you break each idea down into scenes (lets say three), then write those down, you only have 1k words to write for each. And if you write down 3 ideas to include in each scene you then only have 300 words to write on each idea. That's one page. Divide the ideas again if you want - everyone can write 100 words, can't they?
Working this way tends to eliminate blank-page phobia, and provided you spent plenty of time on your outline before you started writing proper you should never be stuck for ideas. Best of luck.