Some people have to be awakened with an alarm clock and others wake up when
they want automatically. In order to do away with your outer alarm clock, you have
to learn how to make use of your 'inner alarm clock.' As you relax in preparation for
sleep, visualize the face of a clock. Mentally move the hands of the clock to one
minute before your real alarm clock is scheduled to go off. After getting good at
waking up at that time, you will have no need for physical alarm clocks.
As a daily exercise, look at your watch, then for the next hour, periodically
guesstimate the time, then afterwards confirm. Then, at odd hours during the day,
catch yourself before you look at your watch and guesstimate the time, then check
your watch to confirm. With enough practice, there is a certain 'knowingness' that
allows you to accurately perform in this manner.