In reply to atreides7887:
I've done a fair amount of experimenting in Scottish winter. here's some of my tips:
1. I wear softshell close-fitting skiing salopettes. Sitting in snow is fine for a while but I tend to sit on my rucksack instead. I only put on the waterproofs when the wind chill gets too high or if its rain / blizzard conditions. If the weather is nice then I'll just wear the salopettes, if its cold and windy I'll wear a base layer under them, if it's stormy I'll take waterproofs too. No snow down the back of your trousers either.
2. Some come with clips, some come with velcro. Clips are fine for all, velcro ones need the trousers to have the right bits to thread through. Why are the trousers falling down? some waterproof trousers have a 'sticky' inside and that makes them creep down as you walk. Try some waterproofs that are lined or slidey inside to stop this. Or get some salopettes.
3. Depends on the gaiter, some have floppy material that can't hold up it's own weight and will scrunch up around your ankles. I find gaiters that are quite stiff don't bunch up, and I fit mine around the top of my calf which helps again.