Second Life and the Mac
(scroll down to the Troubleshooting section for diagnosing and fixing problems)
First off, forget Ctrl-Clicking? in Second Life! Cmd-Click? (Apple-Click) is how it's done here, and note that the Mac Option key is equal to a PC Alt key. If you have a two button mouse you'll find SL a lot easier!
To find a Mac user group, click the Find button then the Groups tab. Type in Mac and hit Search. You can join the group from that window. Other Mac users will be happy to help you out

Based on experience, it seems the lowest Mac configuration that is acceptable for Second Life is a Powerbook G4/iBook G4 1GHZ with 768MB RAM and a 64MB Video card. If you have a G5 with 128 MB of video RAM, some of these modifications may not be necessary. My advice is to start here, and turn things up as long as you don't crash.
Under this configuration and similar configurations the following settings are advisable in Preferences:
Graphics Tab > Performance Options: uncheck all settings except Shiny Objects.
Graphics Tab > Avatar Rendering: Select Normal.
Graphics Tab > Terrain Detail: this is variable, but the Some setting is acceptable.
Graphics Tab > Gamma: Don't worry about this, your Mac controls it. Only useful for full-screen mode, which is inadvisable on a Mac.
Graphics Tab > Display Resolution: Check Run in a window. Don't worry about the settings after that.
Adv. Graphics Tab > Performance Options: Check AGP if it's not grayed. If it's not able to be checked your Mac's video card does not support AGP, which greatly accelerates video. Obviously you want this checked!
Adv. Graphics Tab > Texture Cache Size: This depends on how much total RAM you have. If you have 768MB or more you should use the Large option. Keep in mind that running other applications at the same time as Second Life can reduce the amount of available RAM.
Adv. Graphics Tab > Video Card Memory: Max this out! It only goes up to the total amount of VRAM you have.
Adv. Graphics Tab > Object Detail: Move the slider to the middle.
Adv. Graphics Tab > Tree Detail: Move the slider to the middle.
Adv. Graphics Tab > Avatar Detail: Max it out if you can, but anything at the middle or above is good.
Adv. Graphics Tab > Avatar Vertex Program: This option can cause some problems on some Macs. If you check it and see weirdness (defined as your avatar staying gray, turning bright white or otherwise improperly rendering) for more than a minute, turn off this setting.
Adv. Graphics Tab > Show Avatar in Mouselook: Not necessary, it just shows your avatar's hands etc. when in Mouselook mode.
Adv. Graphics Tab > Draw Distance: In general, 64 meters is good for busy locations. If you want to take a picture of a beautiful scene you can up it much higher. For low traffic areas, 96 is good.
Adv. Graphics Tab > Fog Distance: This feature fades out things that are on the threshold of your draw distance. 1.5 to 2.5 is good for this option. if you have your draw distance down at 64 meters set the fog to 1.3.
Adv. Graphics Tab > Drop Draw Distance if FPS: In the event that your FPS (frames per second, or how fast SL can draw the screen) drops below this number, your draw distance will drop dramatically. Setting this to 0 disables the feature, 3-5 is a good option.
Adv. Graphics Tab > Bumpiness Draw Distance: With enabling Shiny Objects comes Bump Mapping, or making objects and/or avatars appear to have raised and recessed areas. Setting this to 5 - 10 is good.
Adv. Graphics Tab > Max Particle Count: Depending on you Mac you can increase or decrease this. 2048 is a good option.
Adv. Graphics Tab > Outfit Composite Limit: This has to do with how many recent outfits your video card "remembers". If you change your avatar as often as you change your socks, 1 or 2 is fine. If you tend to change avatars mid-sentence, 4 or 5 is a good option.
~~Troubleshooting~~
Second Life stores it's cache files in the following location:
~/Library/Application Support/SecondLife (where ~ is your home folder)
Delete the whole cache folder every month or so to keep Second Life happy, or If you run into slow startups (SL hand icon bounces for a long time before displaying the SL window), strange texture issues and other things.
It is recommended not to run in full screen mode. It works for some but most find it to be more prone to crash.
AGP mode is recommended for all out-of-the-box Mac OS X-ready systems. Avatar Vertex Program should not be used on Macs with ATI video cards (all Powerbooks except the 17", all "iMac" G4 and G5 systems).
Run as few applications as possible while running Second Life, unless you have 1GB or more of RAM.
The Command/Cmd/Apple key is used to modify the mouse instead of the Control/Ctrl key in SL. This simulates the right-click on a PC mouse. You'll notice this will bring up the rotation rings. You can ignore them if you are clicking, they will not get in the way as of version 1.4.
Thanx to Brent Linden for giving permission to copy this
