I run my events with another level 3 judge named Matt Stenger. While at a bar (where all good ideas begin) Matt outlined a new way to try to put together traffic flow for enourmous events like prereleases and GP's (which is good since we are running GP San Diego). It takes a little bit of early effort, but its worth it.
Set up the following tables: Table A by itself, Table B and C relatively close together, Table D off by the dealer tables. Here's what each table does.
This table is the starting sign up sheet table. It contains 1 person minimally, two is preferred. It also contains a Big 2X2 ft sign of a filed in registration sheet, New DCI Cards, and the big book of DCI Numbers, as well as a bunch of Registration Sheets. The Registration sheets are 3X5 inch cards with space for name and DCI Number, with BLOCKS for each letter, kinda forcing each player to write neater. (Think of your income tax forms, that kind of thing.) The Judge at that table helps each player fill out a card and then directs them to table B.
This table minimally uses 2 people, 3 is preferred. These people take the 3X5 card and the payment, and validate its readable. If so, they stamp the hand of the player, and the player is done, nice and quick. Alternate idea is to pass out little chits (pogues are good :P) and collect them at the time of product handling, but its also a pain to do. Depends on your preference. Make sure you have one stamp for each person taking money. Another amazing way to clog up registration is to have the money takers fighting over the hand stamp.
In between table B and Table C stands one judge. This judge continually picks up Registration cards from the people at Table B and brings them to Table C.
This table has the scorekeeper, who does absolutely nothing but type in the cards into DCI Reporter. As fast as humanly possible. :P
This Table has one judge at it, and is used to sell T-Shirts. Because nothing delays a line like someone wanting to pay for the event and buy 3 t-shirts in different sizes. By moving T-Shirt sales to another table you prevent a lot of clog up, same as by moving registration card filling to another table.
Thats it. Its really simple, but really effective. I hope this idea helps at least a little bit...