You need to have a tax ID number
You also need to determine what kind of merchandise you will consign
Collect enough inventory prior to your grand opening that you can get the store going without consigners.
Target your buyers and market directly to them.
Have your consigner contracts ready to go the first day you are open
Set your space up for convenience.
Send a press release to the regional papers a week before you open, use word-of-mouth, rely on everyone you know to spread the word and at least stop in for a visit on the first day.