There are at least 4 types of tickets. Each one of them looks different. This is what I have been seeing on ebay. If any of this is wrong, let me know. Also, I've added seating information.
How many rows are in each deck?
Within the horseshoe:
AA deck - 11 rows
A deck - 37 rows
B deck - 18 rows
C deck - 41 rows
In south stadium:
AA deck - 16 rows
A deck - 40 rows
B deck - 45 rows
Where are the wheelchair accessible seats within Ohio Stadium?
Within the horseshoe:
AA deck - row 11
D deck - row 1
In south stadium:
AA deck - row 16
A deck - row 40
B deck - row 45
What does the asterisk(*) on the ticket next to the seat number mean?
The seat is at the end of the row.
2008 Edition: I've been watching ebay for tickets to the game. So far, I've only seen two kinds of tickets. This may be because students/faculty/staff could upgrade their tickets when they bought them, instead of having to upgrade them during the week before the game. This is my best guess of the kinds of tickets that are out there (at least on ebay).
Alumni tickets/Pres Club:
Upgraded student/faculty/General public
2007 info:
Student/Faculty/Staff are very plain w/ the word "student", "faculty" or "staff" on them. They have a bar code. You need an id to use these tickets.
Upgraded student/faculty/staff tickets are very plain, but don't have those words on them.
Alumni tickets have a nice picture in a landscape format.
Season ticket have a nice picture in a regular format.