I’m still in the planning stages but I intend to use twitter and facebook.  Not sure what good either will do but every little bit helps.  I’ll be doing it for just the purposes you’re thinking of.  

I also want to do a daily blog of my hot dog adventures and pictures of customers.  It will give me something to do if things get slow.  I think it’s important to build “followers” not necessarily on the internet but on the ground.  It’s just another tool.

I see you’re in New Orleans. You are going to be competing with Lucky Dog?
Also, if you need examples on how Twitter and Facebook work in New Orleans, follow Taceaux Loceaux, the Mexican-food inspired food truck.