First off, you need the Crossover application. This application by Codeweavers takes advantage of Wine, and allows Windows applications to be natively run on Mac OSX, inside 'bottles', like different mini-Windows-installations.
Give it a few seconds, and then it'll be created. On the right hand side of the window there are a few options, Bottle, Applications, Control Panel and Advanced. Select Control Panel, and open winecfg.
Once that is open, you can then go to configuring your "virtual desktop", which will allow games to be played in windowed mode, and allows them to run properly on OSX. Switch to the Graphics tab of the Windows-styled window, and tick the "emulate a virtual desktop". I used the size 1024 x 576 for a widescreen window, but you can select whatever in there. Remember that the lower the resolution, the faster your game usually runs.
Now, I installed GTA: San Andreas from BootCamp and then opened it from there, but other Crossover beta testers have reported the installer is working. So, you may pick either. Crossover is pretty supportive when it comes to installing applications, and it should install like it does on Windows.
Sounds like a good guide, I am in the process of trying it out. I have installed GTA San Andreas on Cross Over before and the game ran ok however it was prone to loads of graphics glitches and errors, perhaps your method will eliminate these!
I tried your guide, and on my hardware I am still getting way too many graphics glitches to be able to play the game really. I mean its not too bad when a building or tree is slightly messes up but when the glitches make it so you cant see where your going or who your following, etc etc.
I did read about SA-MP being successfully installed on wine on a linux machine, I have not ever played SA-MP as I keep my boot-camp partition isolated for its own protection. With San Andreas running as well as it is now, I would have thought it would not take much more to iron out these small graphics problems.
So i tried your "guide" and gta starts i see the sound logo and Nvidia than i see the gta loading screen for a few seconds than my screen turns black than very quick blue and than goes back to mac. what the hack? the game copy works fine in windows xp.