Source games are known to handle rejection poorly. When minimizing or Alt-Tabbing out of them, they often freeze up or crash. What are some tricks to minimize the pain?
I play full screen mode windowed. All the gfx without the minimizing.
Assuming you are playing these games through steam, a possible approach would be to avoid minimizing as much as possible by relying on steam's in-game overlay (launched by pressing Shift+Tab) as much as possible.
Seeing how the overlay supplies a web browser, you can do quite a few things while keeping the game in the foreground.
It's a pain and there is not much you can do.
If you already know that you need to do some ALT-TAB while playing (because your are following an internet guide, chatting with some friends not in Steam, etc.) just start in window mode.
You can set different launching parameters: more info here.