It's usually music with me. I like to listen to music because it helps me develop a certain mood that helps me write. I like to put in some personal events and change them up a bit. Or sometimes just put things that have happend to me and make the character experience it. If that's what you mean by the whole girlfriend/boyfriend thing.
It used to be that I had to have music on. Like soundtracks and such would really get me motivated. But now, it turns out that I need absolute silence to write. The only time I listen to music is whenever someone is being loud in the house and kills the sanctity of silence, so I blast my iPod in return. With headphones on, of course.
I also find that I can't write well in the morning. It's weird. Maybe it's because I'm groggy or something. As for the mood, I have to be calm. If I'm angry or sad or something, I can't write. My mind is focused on too many things then.
I tend to work well with music in the actual writing, and I often get a lot of ideas on the spot during that too. But it's more just a general 'I want to write rather than ____' feeling - can't be too tired or busy for it and beyond that it's really just whether I want to write or do something else.
I just kind of decide to write, and I do. I carry a notebook around with me wherever I go, so if I have a few minutes here and there, I write if I feel like. When it's time for me to sit down and write for a longer period of time, sometimes I like silence, sometimes I like listening to music. There's no set way to put me in the mood to write.
Just reading other's work sometimes will do the trick. Read and then think about how you would continue the story or what you would have done instead. Be careful about writing things that are too closely related to your inspiration though. I like silence when I write.