In regards to underwear, I have found ove rthe years it depended on the quality of overpants i had that determined what I wore underneath. The overpants I have now, have zipable vents so temeprature control for me in improved. If you over pants do not have venting, something of a performance wickable longjohn stype is probably prefered. Helly Hanson makes some good base layers. If you are going on the cheap, I have used flanel pyjama pants and was quite comfortable. I have also used sweat pants, but these tend to hold mositure on major temerature swing days.
What I wear now - there from Canada, and you can look for them online - driWear Microfleece thermal long underwear, but like i said, my pants have controlable venting, which helps maintain my temperature balance.
Question of socks: Merino wool, and as one other commentor mentions above - socks only into the boots, no tucking in the long underwear below the top of the boot - trust us on this one!
Another commentor mentioned about drying the boots at the end of the day - This is the most important thing you can do to enjoy a follow-up day out on the slopes, but unfortunately many forget to... I would ask whomever you are renting from to show you how to remove the liners from the boots for drying - simple process, and it will get those sucks dry as a bone for the next day out.
Enjoy - and Cheers, for your great white neighbour to the North.