Opening documents on an Imac

My imac g5 goes to Microsoft Works as the default application for opening documents and email attachments. I want to use NeoofficeJ. How do I change the default application?

Right Click (or cmd+i if you don’t have a right mouse button) on any example of the filetype whose association you with to change. One of the options in the menu that pops up will be ‘Open With’, click on the arrow to the left of ‘Open With’ if its not already pointing downwards. Then just select the program you wish to use from now on from the the dropdown menu, and finally click on ‘Change All’

Small correction: If you right-click (or control-click), don’t choose “Open With” but choose “Get Info”. From that window follow xiix’s instructions. (Otherwise, you don’t get the “Change All” button.)