In Louisiana, each voter:

1. Presents a photo ID or other acceptable ID (there is a fairly extensive list of permissible substitutes, but virtually everyone has a drivers license or a state-ID for non-drivers), and

2. Signs next to their name in "the book," which is maintained and provided by the local Board of Elections, listing all eligible voters in a given precinct. If your name is not in the book, you can't use the voting machine in the booth, but you may cast a paper provisional ballot.

This book is NOT "federal" here and the situation is probably the same everywhere in the US. The fact that it is maintained locally should mean that it's pretty reliable. Newly registered voters are always in there, and those who have already voted absentee or early are clearly crossed out.

In New Orleans, there are more names than probaly should be on the rolls, rather than fewer. There have been efforts to eliminate the names of those who left with Katrina and have never gotten back, based on mailings returned as "not at this address," but the voters in question have not been deleted. They just have a notation at their names in the Book, requiring address verification and a signature on a form asserting that the informatin is true, etc.

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Several people have voiced complaints that provisional ballots do not get counted. That's usually true, but only in cases where they don't matter anyway.

Counting provisional ballots would be a huge pain in the ass. If the number of provision ballots is less than the margin of victory in every race on the ballot, they are (quite correctly) discarded.

If the number of provisional ballots is equal to or greater than the number of votes separating the first-place and second-place condidiates, then they WILL be counted. Even in cases where every single provisional ballot would have to be for the same candidate ~ statistically unlikely ~ in order to affect the result.