Serendipity, wow that's both a very difficult word to say or write for me. The guys at Wikipedia describe this word as:
(...) the occurrence of an unplanned fortunate discovery. Serendipity is a common occurrence throughout the history of product invention and scientific discovery. — Wikipedia
Randomness helps a lot in finding ideas. Many people find solutions to their work problems under the shower, or when they are walking their dogs. Either you stop thinking about the problem and that's when a solution comes. Or you mind just wanders in random thoughts that then serve as an inspiration to solve the problem.
Nothing like a nighttime stroll to give you ideas. — J. K. Rowling
So when it comes to idea generation, the context where you are matters a lot. If you are looking for new ideas in your old office it might be quite hard as the context just reminds you of all the other work you have to do, and all the stressful situation you experience there.
Many people just go for a walk. And it works. When I have to find new ideas for my books, I either go for a walk or take the train for a few hours. By being in a train and looking around myself I see many elements that create random thoughts: a building, an element of conversation from the people behind me, the style of the jacket that someone is wearing. These create different thoughts that then bring me to different ideas at the end.
So context matters a lot. It's hard to come up with good ideas in a space where there is no light and everything feels depressing. It's much easier to find new ideas when you are sitting in comfortable chair in a beautiful café, with a hot chocolate and some jazz music in your hears. At least, that's my very personal experience.
So, create a context that pushes serendipity and puts you in a positive mood that enables you to be creative.