Puzzle #9 - The Snail

It’s been a while since I posted a nice puzzle and since I know they are so popular, here is a relatively simple one. It was used in job interviews btw (the last line will boost the amount of views for this post…)

A snail leaves his warm house and takes a crawl through the forest leaving behind him on the ground a trail of “0″s and “1″s. He takes a very complicated route crossing his path several times. At one point he becomes tired and disoriented and wishes to go back home. He sees his own path of “0″s and “1″s on the ground which he is about to cross (i.e. not the trail ending in his tail) and wonders whether to follow the trail towards the left or towards the right.
What is the shortest repeating code of “0″s and “1″s he should leave as he crawls in order to easily and deterministically track the way back home? What is the minimum amount of bits he needs to observe (or the sample length of the code)?