When dining alone, I prefer to eat at a place with bar service, so at least you get the chance to talk to other diners or the bar staff who are normally friendly. Some of my best experiences while travelling around the US a few years ago were just rocking up to a bar, ordering a burger and chatting to the guy next to me.
Back home here in Melbourne, I ended up going to one place a fair bit to eat and ended up getting invited out with the staff for drinks one night. Sure it may have been pity, but so is much of my sex life.