At The Last Minute I've received lots of e-mail asking for tips on how to get tickets. Just go to a company's booth and ask them.
Some vendors still have tickets available on the day of the party.
I usually do pretty well by striking up a conversation with a booth staff member, and then nonchalantly asking them if they have any tickets left. Apply a little social engineering to the person at the door. Confidently stride up to the door, flash your business card, smile, and ask. This will work if the aforementioned door person is an employee of the company. Go with people who have tickets.