Photographing snow?

I seem to get underexposed at times when i photograph snow, the thing is i don't notice just by looking at the picture on my camera LCD.
Whats worse it's not all the time i photograph snow just in some situations, there's the exposure graph in the camera i tried to use but i can't make heads or tails of it when it shows two huge spikes andthat one of those will be either under or overexposed if i change the exposure.

Help

With snow, you have to realise that it will underexpose (and look grey) due to the nature of the metering.

What you need to do is meter on the snow and overexpose the snow by approx 1 EV for it to show as white.

As for the histogram, one of the "spikes" (the right hand one) will generally be the snow. So long as you dont push the spike past the right hand edge (at which point you lose detail), it will be correctly exposed.

It helps if you first decide what highlights you need to keep, & which ones you can safely allow to blow out. You should think about shooting on manual as the snow will throw the meter off, like the sky does in this: Post #47
Click the "post #47" at the top-right of that post if you'd like more info on the subject.

Basic theory of metering: A meter tries to take an 'average scene' and render it to 18% tonality...so if the item is white or black, the meter suggests a reading which would render the white item as 18% gray, or would render the black item as 18% gray!

Corollary to basic theory of metering: If the item is not 18% gray, or the scene is brighter/darker than the 'average scene', you need to dial in exposure correction (EC).

Snow can be difficult to get the hang of and, as has been said, you need th overexpose a little. Add to that, it tends to change color with the light, ie, red tinged in the morning, blue in evening and white in mid-sunlight.
Adjusting those quirks in PP is a relatively simple process.