I tried to get tickets for the launch on 14 May this year; although I made it into the website "waiting area" when the tickets were released, the website was overloaded and I missed out.
There are tour companies that get an allocation of tickets, and sell tours to the viewing locations; these are more expensive, but may be easier to get. But you should find out when they go on sale, and plan to buy them immediately (i.e. the hour they go on sale).
Since I missed out on tickets, I just drove up to the beach about 5 hours early in the hope of finding a good spot. Here's a map of where I was, with the parking area marked, as well as the spot on the narrow sea wall where I actually watched from:
Space Shuttle viewing - Google Maps
The spot is 12 miles away from the launch pad, but you still get a good view. Don't expect to hear the launch -- it'll take the sound about a minute to get to you, and even then it won't be very loud. Here's a picture I took of the launch.
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You should plan on doing a Kennedy Space Center tour the day before the launch, so you can see the shuttle on the launch pad from just three miles away. The ticket to KSC is good for two days, so you can see all the other exhibits on a second day.