These are my five favorite personal running form cues. When I say personal I mean they work for me, and have worked for the few people I've shared them with. Maybe you will find them helpful as well.
5. Easy, light, smooth.
Straight out of "Born to Run". I always try to keep my footsteps easy, light, and smooth. No pounding allowed. this one is also known as "run like a ninja".
4. Unicycle wheel.
An extension of number five. When I am really in the zone, my feet feel like they are attached to the wheel (not the pedals) of a unicycle. Ground contact, moving through the stance and lift off are all one smooth cycle.
3. No Frankenstein, but no zombie either.
If I feel like Frankenstein's monster I'm doing something wrong. I don't want to shrug my shoulders upwards while I runk, I don't want to much tension in body parts that don't need tension. This cue also helps me not clench my jaw. I also don't want to get too loose and have body parts like my arms flopping around when they shouldn't be.
2. Six shooters.
I want my arms to swing as if I am shooting at the bad cowboys with my six shooters, past the hip, then in a straight line in front of me. Not across the body, that would be shooting like a stormtrooper.
And Finally. . .
What really gets me in good posture is this. When I'm near the end of a hard run, and I'm tired, and achy, and ready to be done. Out on the road or on a trail all alone in my own head, then off in the distance I see another runner. That posture my body certainly adopts at the instructions of my ego, that is good posture.