Visit Visa Application Center – The Process

VAC is the center where you’ll be completing your document verification, bio-metrics registration and photo.
Before proceeding to VAC, please make sure that the details you have in DS160 application exactly matches with your passport details. Name should at least match exactly, I’ve seen the staff comparing names character by character.
To start with the process,

• Reach about 15 mins before the appointment time
• The required documents are confirmation page of DS160 application, visa appointment confirmation page and your passport.
• No other document will be asked usually, unless they find some discrepancy.
• You enter the queue outside the center.
• Security check will be done at the gate. Only documents are allowed.
• Documents will be verified on the next stage
• Post verification, a sticker with bar code will be pasted on your
• Next, you’ll be given a token for the counter. At your turn, go to the counter.
• The operator will register your finger prints and photo into the system. You will also take an oath that the information is correct and true and tada tada tada. 
• Guess what, you’re out!

I found their process terrific. There were no unnecessary waiting periods or delays.
Also as a reminder, you’ll need to complete process at VAC at least a day prior to your visa interview.