totally i agree, when i used to go to motels selling my software i made sure that my appearance(most importantly) was perfect. Make sure you do the obvious:
Where something business like(ie, suit/tie)
Comb your hair
Talk friendly(don't right away say, "Can i speak to your manager please)
Then be sure that you have brochures, business cards, and flyers(yes all 3). All these should be full color(I've seen people try to buy me with black and white), and professionaly made. I suggest you spend between 10 and 15 percent of your expected profit on handouts.
If there is no one there to talk to, leave YOUR contact information, do NOT ask for theirs. It will make you sound too pushy, which is one thing you do not want.
If they do not make contact with you in 24-48 hours, then and only then should you call them back with a follow up call.
As a salesman, I always tell the customer the facts. I don't suggest referring to information in the brochures, so you shouldn't say things like "As it says on the bottom of the flyer..." or stuff like that.
If you are too pushy, they will think you are desperate for their business-which is not want you want them to think...