Alternatives for load balancing Tomcat webapp?-Collection of common programming errors

We wish to enable some form of load balancing for a Tomcat webapp we’re currently using today. Unfortunately, I know almost to nothing about Tomcat load balancing, clustering and so on.

Can anyone share resources that cover the different alternatives, give some handy pointers (maybe some solutions work better in certain types of environment?) or just some tips on solutions to try out? We’re currently running Tomcat 5.5 if that makes any difference in features, however no critical obstacles for upgrading to 6.