Cuppa tea and some music puts me in the rights usually. I also check the prompt at the beginning of my day (or, during NaNo, read my last couple of paragraphs) and then stew on it during my work shift. That way, even if I'm grumpypants when I sit down to write in the afternoon, I at least have the start of what I'm going to write ready to go.

If all else fails, I strike up a chat with someone I don't actually want to chat with. That way, eventually there will be a tipping point where plodding through words is preferable to this awful conversation.

I wish I was joking about this.