I'm with you here. I have a hard time remembering keyboard shortcuts as well on the Mac because they generally different than the corresponding shortcuts on Windows. It turns out that unlike on Windows on the Mac its pretty easy for a developer to write an application that goes through all the menus and sucks out the keyboard shortcuts and let you look at them.
There's a very simple application that I've used called Cheat Sheet that does exactly that. If you press and hold the command key on a Mac with this application running you'll get a pop-up that displays a list of all the shortcuts for the menus in the current application you're using.
It's really helpful because otherwise you'll have to dig through all the menus to find the shortcut keys so I suggest you take a look at Cheat Sheet. It's a free application and I found it very useful. There are other applications that do the same thing and also provide more features so you might search the web for "Mac keyboard shortcuts" for more information.