Trying to get PAX tickets is a horrible experience. Four-day passes sell out within minutes, day passes within a few hours. PAX intentionally does not announce ticket sales ahead of time as they believe it cuts down on scalping.
The best way is to follow their Twitter and set up to receive notifications when they tweet. They'll announce within a few minutes of putting the ticket sales up, so just be ready. They usually go on sale on a weekday morning in May.
However, this year's are sold out. So now the only way to get one is secondhand. The most reliable way to is see if someone you know bought extra. You can also try Craigslist or eBay, but those are always kind of sketchy. Keep in mind that badges haven't been sent out yet, so anyone claiming to have it on hand already is a scam artist.
In the future, try to find a group of people who are also interested in going and have everyone keep watch. That way at least some should be able to buy tickets and hopefully get enough to cover everyone who wants to go.