If I want to write, but find myself really stuck for ideas, I browse the NaNoWriMo forum. In the "Adopt A..." threads, people post their rejected ideas for plots, characters, titles, lines and so on. There are some real gems hidden in there.
As for countering writer's block yourself, the best advice I can give is to not think too hard. Ideas will usually come when you least expect it, so be sure to keep a pen and notepad with you to jot down any new ideas. You may also get ideas from watching TV and films, and reading books. Just watch/read to a certain point (such as the end of the beginning) and then take the story in your own direction. All you have to do then is come up with a new beginning!
I find listening to music a great source of inspiration. A lot of songs have a story behind them. Others describe a feeling. Listen to any song, and put your main character in the situation it is describing. How did s/he get into that situation? Is s/he going to get out of that situation? If so, how? Or does s/he want to be in that situation? Then how does s/he ensure that s/he is going to stay there? How long will s/he be there for?
You can also take ideas from real life. People-watch. Observe their actions and their conversations, and try to imagine what's happening in their lives right now. Read newspapers and magazines. You could read the problem page and ask if your character could have Joe Bloggs' problem. Does s/he solve it, or come to accept and live with it? How?
Ideas are everywhere. It just might take a bit of time .
I close my eyes to see a sight ahead,
An everlasting dream,
That makes me wake to find myself
In my own eternity...
I would suggest listening to music. That always gets my writerly juices flowing. Maybe watch Tv, sometimes that triggers ideas, or play a mindless game like solitare. I don't know why, it just makes ideas come to me. Good luck.
Ask the question "What if...?" or "What would it be like to...?" once a day. Write for five minutes. Who knows, you might find the germ of an idea buried in there somewhere.
Writing, like any creative process, takes time and patience. Whatever you do, don't go idea-hunting. That never works. When I write poems, I let the idea come to me and mull around in my head for a while. You need to let the idea do its own thing. When you feel it's ready to be committed to paper, do it. Trust your instincts. You might be surprised.
"Don't bother just to be better than your contemporaries or predecessors. Try to be better than yourself." William Faulkner.
Do you do poetry? Check out Poetry Inspiration over in Groups!
If you haven't already done so, write down the plotline.
Write on impulse.
Relax, do yoga, whatever makes you feel calm.
Don't worry about writing in sequence. Write random parts that come to mind and fill the rest in later on.