How do I sync games save data across different computers?
There are really two answers to this question, and they depend upon how the game is made.


If your game is using Steam's Cloud service, your save games will be automatically copied across your machines. Here's a PC-centric probably incomplete list of games that use Steam Cloud. Not very useful, but the best I could find.
Most non-Steam games will create a file somewhere on your Mac which contains your save data. This save file could be in the game directory, it could be in your Library folder, it could be elsewhere. That's going to change depending on the game, and is up to you to find out. We can sync this file via Dropbox.


Now, if the game lets you choose where to place your save file, you could save it in your Dropbox folder, and let that sync it across devices. Just make sure it's fully synced on every device before loading it.
If the game doesn't let you choose where to save, we're going to have to do it manually. We need to create a symlink, which is kind of like having the same file exist in two places in your filesystem at once. Time Machine makes extensive use of it. Lifehacker have a post detailing using symlinks to sync files and folders for Dropbox. Now, I haven't tested it, and you should be very careful with this. What you want to do is to open up Terminal and do something like this:

ln -s /Users/PutYourNameHere/Library/Preferences/com.nakiwo.doukutsu.plist ~/Dropbox/MySaveGames/CaveStory/com.nakiwo.doukutsu.plist



You're going to need to replicate that on both computers. Now, be very careful with this method, and make sure you back up any files you try this with. I'd be very, very careful about doing it with whole folders, especially important ones like the Preferences folder. But in theory, it should work. Good luck!