This is my first tutorial, and I may know that there are others tutorials like this in the forums... Let's get started.
1. Download Second Life Beta Viewer
2. Install it and it will ask to run when finished. Click 'No'.
3. Look for the icon of the viewer and right-click it and select 'Properties'.
4. In 'Destiny' texbox, look for the end of the path.
"C:\Program Files\SecondLifeViewer2\SecondLife.exe" --set InstallLanguage en
"C:\Program Files\SecondLifeViewer2\SecondLife.exe" -loginuri http://osgrid.org:8002 -loginpage http://osgrid.org/loginscreen.php -helperuri http://osgrid.org/
Now, login with your First Name and Last Name and Password and have fuun!