The theme of February's RPG Blog Carnival is How and Where I Write and/or Game Prep.
I improvise a lot during my sessions. But you do need some prep, even if it's only coming up with non-ridiculous character names or some cool photos of locations as inspiration. We play weekly, so I do bits and pieces whenever I find time, mostly on my laptop, where ever I might be at the moment. It all gets transferred to my tablet and/or sheets of paper stuffed into the rulebook and that I take with me to game night.
Actually coming up with ideas for scenarios and adventures is the hardest part for me. That's why I do most of that at the breakfast table with Mr Bookscorpion. He's a gamer himself, but I don't think that this is strictly necessary. I would just need someone willing to listen and to think about how the story could go. I throw ideas at him and he makes suggestions. Whether I take those up or not, explaining the situation to him and talking about where the group could be headed next helps a lot. Usually, I think about what we have come up with for the weekend, turning it over in my head until the rough edges are gone and then I go ahead and start the actual game prep.
The Carnival is hosted at Leicester's Ramble. Age of Ravens has a short survey about game prep, so if you have two minutes (six questions only), why not go and take it!