<p>I currently have Apache HTTP Server, but I'm guessing I'll need Tomcat (and then have to configure it in a way that makes it not open to the public), a Java JDK (which I already have, but should probably update), and an IDE (I have Eclipse). But what else should I have or know before starting?</p>

I would go for maven.
It will give you a quick start in configuring your project (by using archetypes) and it will manage your dependencies.
Install it and run the archetype command to create your project.
```
```
mvn archetype:create -DgroupId=com.mycompany.app -DartifactId=my-webapp -DarchetypeArtifactId=maven-archetype-webapp
```
```
After that just use the maven eclipse plugin to configure your eclipse environment for that project (
http://maven.apache.org/plugins/maven-eclipse-plugin/
).