How do aircraft land on snow?
It is very common for planes to land on snow (i.e. packed snow) or even ice runways.


  How are planes kept in control with so less friction on ground?


Snow/ice friction is a function of the outside air temperature, so it depends. Another factor is whether the runway was packed, fresh snow - and the temperature the previous day. The colder it is, the more friction the snow will have (i.e. adequate braking). In warmer temperatures the snow will be slick (scarily slick at times - as in nil braking).

While flying a multi-engine airplane, one can use differential power. If you're flying a single-engine airplane - one is better off with small taps on the brake during slick conditions. If the OAT is relatively cold (well below freezing), braking can be pretty good.


  What is the procedure to perform such kind of landing?


The procedure is the same as a standard landing. However, it is awfully nice to have good contrast on the snow to see the runway. Often runways that are pure snow/ice will be more visible than the surrounding terrain. At the very least - the runway will be outlined with some sort of runway markers.


  And, on an average how much extra distance does an aircraft 
  covers by landing on snow, as compared to landing on ground?


As I said before, it is really dependent upon the outside air temperature and the condition of the runway (i.e. packed snow or fresh snow).

For example, suppose there were fresh snow on a relatively warm day (30 degrees farenheight) and the snow is compacted (i.e. by humans) that day. Say, night-time temperatues drop to 0F, and the next day you land with an OAT of 30 to 35+F... that runway is going to be SLICK. However, if the temperatures were to stay at 0F - you would actually have decent braking. Even further, if the OAT dropped to -40 below...you will have excellent braking.

TLDR: 

Snow conditions are always changing and braking/control of the airplane are dependent on those conditions. Snow-conditions are highly dependent on the outside air temperature and to some degree human-maintenance (for better or worse).

*source: Personal experience from flying in the Arctic.