Actively gather stability information as you travel.
Frequently step out of the track and "feel" the snow under your skis or feet. This can give you an idea of what the upper layers are composed of.
Poke your pole into undisturbed snow and "feel" the layers in the snowpack. When you poke your pole in, do you feel harder snow on top of softer snow?
Is there a crust? Is the snowpack shallow or deep?
Be constantly alert and observant as you travel.
Imagine yourself as a wary cat keenly atuned to its environment. Consciously and deliberately gather stability information throughout your tour.
Watch for recent avalanche activity. It is a sure sign of instability.
Wind slabs are dangerous. A wind slab will often sound hollow or drumlike as you step on it. Wind pillows can look like a deep, sweet pile of powder. Either way, the structure of the snow pack is different in a wind-loaded area, and you need to examine this if you are going to cross or descend a wind affected area.
Cornices are the bombs of the back country.
Kicking and releasing soft small cornices can help test the surface stability of the slope below.
Use caution where you stand: cornices often break back further than you think.