I love this part of OS X. I have things set so that different types of apps open in different spaces. (I work with 8 spaces-each has a different type of app associated with it)
Using CMD+Tab works in conjunction with this setup. Otherwise, CMD+tab alone, won't open specific application windows if you're in a different app, and the one you want is minimized. Well, it can be a bit inconsistent really. But how you can be sure to get to an open window, and not just see the toolbar menu...
Do Cmd+tab, but when you land on the app you want, release the tab key, then roll your finger off of the cmd key while at the same time pressing the alt/option key. This technique is good when you don't have spaces and expose set up together. Otherwise, if you do... you can just cmd+tab to an active app.
Where it's inconsistent (for me anyway.. others feel free to test and chime in) is if you have an app minimized. In this case, you'll have to do the trick I mentioned (roll off cmd while pressing alt/option) and that will restore the window to an active position rather than having it be minimized and you're only able to see the menu but not the window.
I really hope that didn't confuse you! It's easier to show in person I guess.
Doug