In outlook of the source machine choose File then Import and Export
Choose Export to a file and the type of file will be Personal Folder File (.pst)

Choose which folders you wish to export and tell it where you want the pst file created and click Finish. (Keep in mind when you go to import you will be able to choose what to import so I generally export everything and then pick and choose on the import side.)

Now on the destination Outlook go to File then Import and Export
Choose Import from another program or file scroll down and locate Personal Folder File (.pst)
Choose the folders to import and go.

The menus will vary depending upon which version of Outlook you are using but the steps are the same.