Originally, the tiebreaker was as follows:
All of the castaways EXCEPT the two who are in the tie get to vote a second time. If the vote ends in a tie again, then it goes to a discussion and the tribe has to decide, unanimously, which of the two goes home. If they can't decide and it's deadlocked, then they draw rocks. All the castaways - except the immunity holder and I believe the two who were voted for (they become safe) - draw rocks and the one with the odd rock goes home. I THINK.
This year they're doing the tiebreaker differently. If there is a tie, there will be no re-vote and they will go right to discussion to try to come up with a unanimous decision. Then I assume it goes to rocks if necessary.
I'm an admitted Survivor junkie and have watched every single season no less than 3 times each. (In my defense, I went through chemo and multiple surgeries in 2007 and 2008 so I had a ton of time on my hands and terrible long term memory...also, I love Survivor)
Ties have been dealt with in different ways over different seasons, like the show has evolved, so have the rules.
Season 1: as far as I know there were no rules for breaking ties and the tribe would have to keep voting until the tie was broken.
Seasons 2 and 3: Ties were decided by previous votes against which is one of the reasons why in Africa it was a huge deal when the tribe switch happened, if it was known who had votes cast against then strategic voting could occur.
After that, ties were dealt with by first a revote with the tied people not voting. After that, if it is still a tie then they are considered to be deadlocked. At this point, the people who do not have tied votes have to unanimously agree or draw rocks...unless they are at the final 4. Final 4 deadlocked votes go to a fire making challenge. Also, there has been one time that a firemaking challenge was used instead of voting. In Palau when there were only 2 people left on the Ulong tribe.
As a side note, the funniest (saddest?) fire making challenge was final 4 for Cook Islands. No one know for sure how long it went on for but it was close to 2 hours and when the producers finally gave in and gave them matches, one of the players actually ran out of matches!
Survivor Funny 115 has a pretty amusing write up of this.
Oh, one last thing...most confusing tie breaker ever (IMHO) was the final 6 vote in Cambodia. Because of a combo of individual immunity and hidden idols, there were no valid votes. After a tied re-vote, Keith had a choice of either changing his vote or he would go home by default. (3 people with immunity, 2 people with tied votes against which leaves only one person to draw rocks.)
Well, there you go...everything you never really wanted to know about Survivor tie breakers.
