Source: Mentalfloss.com, 7 Ways People Woke Up, Pre-Alarm Clock:
1. BLADDER CONTROL
Early man drank tons and tons of water if he needed to wake up before the sun. Why? Well, if you're over the age of 30 or so, you probably know what getting up in the middle of the night to urinate is all about. The custom of "over-drinking" before bed was even utilized by Native Americans well into the 20th century.
2. THE CLEPSYDRA
Speaking of water, the clepsydra, or water clock, was used by the earliest civilizations for thousands of years. They weren't so much clocks as they were timers, working in much the same way a common hourglass works. It wasn't until 245 BCE that Ctesibius of Alexandria improved the clepsydra, or "water thief" as it was known, and created the world's first mechanical clock. It's mind-boggling to think about what Ctesibius accomplished: Seasonal cycles required irregular water levels be dispensed into a receiving vessel with equidistant hour-marks, while daily cycles required varying hour-marks and regular efflux. Making the clepsydra an alarm clock required nothing more than a floating bob that struck an alarm once it reached a desired level. Later versions turned gears, signaling an alarm or even springing a catapult that launched a pellet into a metallic plate.
3. RELIGIOUS WAKE-UP CALLS
In many early Christian societies, bells called churchgoers to prayer in the morning. Religious bells also served to mark the passage of time throughout the day before people wore watches. In most Islamic traditions, audible tones and prayers marked the start of the day (just as they do today). The Fajr (literally "dawn") is the first of five daily prayers blasted out through the village. Four more prayers follow the sun and help mark the passage of time, day in, day out.
4. PEG CLOCKS
About the year 1555, Taqi al-Din Muhammad ibn Ma'ruf invented a few different types of mechanical alarm clocks, including one that would sound at any desired time. This was achieved by placing a peg into a hole on the face of the clock. Taqi al-Din was born in Syria and schooled in Cairo. Similar clocks were also developed around the same time in Western Europe.
5. THE KNOCKER-UP
The Knocker-Up (also referred to as a Knocker-Upper) gained prominence during the Industrial Revolution, using a long stick with wire or a knob affixed to the end to rouse customers at a desired time. Clients would agree verbally in advance, or simply post a preferred time on doors or windows. For a few pence a week, clients could rest assured knowing their Knocker Upper would not leave until he (Knocker Ups were almost always men) was certain a person was awake. Larger factories and mills often employed their own Knocker Ups to ensure laborers made it to work on time.
6. THE FACTORY WHISTLE
At the dawn of the Industrial Age, workers lived around the factory at which they worked, and would wake at the sound of the factory whistle. Steel and textile mills drew in farmers from the countryside, and like that, ding-ding, the clock ruled the roost. Time was always money. But now time could also be regulated more easily. Work was no longer driven by the season; rather it was divided into units of time. It was the factory whistle, not the rising sun or the chirping birds, that called people to work.
7. LEVI HUTCHENS'S 4 A.M. ALARM
In 1787, Levi Hutchens of Concord, New Hampshire, invented another incipient alarm clock. Built into a simple pine box, a gear mechanism set off a bell. However, the bell on his clock could ring only at 4 a.m., not coincidentally the time Levi needed to get up for work. Finally, on October 24, 1876, a mechanical wind-up alarm clock that could be set for any time was patented by Seth E Thomas.