You can easily set up environmental variables which needs to be available globally for all your applications. This can be done by placing scripts in the /etc/profile.d directory which are executed every time a shell instance is being created.
Example: To set JAVA_HOME environmental variable so that it points to where you have installed java, you can either create a new shell script or edit an existing shell script in the profile.d directory. Type in the follwoing line and save it as java.sh in the directory
JAVA_HOME=/usr/java/latest
You are done. Now every application will know where you have installed java. Now that is one of the easiest things you could do in Linux 🙂