How did people wake themselves up at a specific time before alarm clocks?

by Hmez
mef08d

This has been answered a few times:

http://www.reddit.com/r/AskHistorians/comments/1q0vi2/how_did_people_wake_up_at_set_times_before_the/

http://www.reddit.com/r/AskHistorians/comments/1k0ubr/before_alarm_clocks_how_did_people_wake_up_on_time/