Next step, you need to adjust hardware options. Cmd-P
(CTRL-P on Windows/Linux) to bring up Preferences, then click on the Graphics tab. Now click on the Hardware Options button. You should then see a slider for
Texture Memory. Make sure that's set to no more than half of the total amount of video memory in your machine
(up to a max of 512MB). If you don't know how much video memory your computer has, setting to 128MB is ideal. If you run other programs at the same time
(especially big graphics apps like Photoshop), you may want to set the number to a lower value. If you've ever experienced graphics glitching or screen flickering before your SL Viewer has crashed, that's a telltale sign that your Texture Memory setting is too high.
In that same window is a setting called Fog Distance Ratio
(Note: for some machines this setting is grayed out - if that's the case, skip ahead). It tells SL how far away to make the horizon foggy/hazy. Lowering the number can improve performance greatly by making objects in the distance get hazy/foggy. On my old computer, I set that number to 2.0 and it really made a difference all by itself. Close that dialog by hitting Okay.
On the main Graphics tab, click the button marked Advanced to show a tangle of additional graphics settings. On Viewer 1.x, instead of an Advanced button you'll see a little checkbox marked Custom - tick that to see the additional options. Here are my suggestions on changes to make.
If your machine is older
(or Windows/Linux users on a low end laptop or netbook), uncheck Hardware Skinning
(while newer machines will want to check the box). It tells SL to have your graphics chip handle the process of rendering skins.
Avatar Impostors is a subjective choice. Turning it on tells SL to use pixelated bitmaps called sprites
(similar to old Super Nintendo game characters) to draw the avatars further away from you, instead of rendering each one
(with all their attachments and bling). Turning it on speeds up performance, but doesn't look as nice. If you do enable Avatar Impostors, then the slider on the right for Avatars lets you adjust the distance SL uses to switch things out. Go to a club or someplace crowded and play with this setting :-)
Make sure that your particles slider is 4096 or less. If you're really having performance issues, you can drop that down to 2048 and still see plenty of sparkles, poofs, and flame effects.