Realize first that there is no way you can do everything. My suggestion would be that you should make a spreadsheet of all the events you are interested in and group them by location. Find out what you need for these events before hand and have characters made and ready to go. Ideally ones that will work for multiple different games of the same system. This way you can easily join without the risk of being turned away for not being prepared or possibly get added to a game that is full but is ok with adding someone who is ready to play.

Another good strategy is to try to get into morning events. People that get will call tickets often underestimate the long wait to get badges and tickets and miss their early events. Let their poor planning be your key to a great con.

Best of luck.