I spent 2 years working in the cabin on a bus and got myself into a habit early on to tap the arming lever twice with my hand before opening the door. The lever should stay in the 'up' position as the pin is in place to prevent it from moving. At the same time I could be looking outside to just check there really IS a platform there and that I wasn't hearing knocks that weren't there!
It is easy enough to blow slides and I know a couple of people that have done it, particularly after a long tour of duty. However since we know that crew (being human) are susceptible to this it might not be a bad idea to develop your own personal habits to do your best to ensure it doesn't happen to you!
Just a thought, safe flying (and door opening!) y'all...
FJ2k