The easiest way is, pick a random door in the first room, and then every time you come into a new room go back the way you came (doors aren't symmetric in this game.) This will put you in a cycle that eventually takes you to Rick. You'll visit some rooms more than once.
Alternately, just stumble around until you find a room with one top entry and 3 bottom entries. Take the bottom left door, which will take you to Rick.
