In my personal experience, I haven't deliberately forced ideas, however that could potentially work.
One thing may be to become aware of when you have ideas - I've found I have my best ideas when I'm not sat at my laptop.
The ideas for my two startups came when I built something for myself and found that others wanted it too. These were little problems (at first).
I think a final important thing that comes to mind is that if you have even a twinkle of an idea, then grab onto it with both hands, and work with it. My latest app was a tiny idea and I developed it in just over a month and a half into something of value and I've now just had my first customer. Work with the ideas and eventually you'll find yourself swamped with things to build upon that single idea.
Hope that helps.