There is a difference between what is best for your health and what is realistic to implement in your life. The amount of sleep you need is different for everyone.
Ideally, it's best to go to bed when the sun sets (or little after) and wake up every day without an alarm clock. I did this for a month every day and felt amazing, but it does impact your social life. So I stopped doing it that extreme.
More realistic would be: get at least 7 hours of sleep during 'work days'. (7 hours is a good duration for most people. But you should experiment with this and find out what works for you.) Try to go to bed about the same time every 'work day'. On weekends, try to keep to this schedule as much as possible. And wake up without an alarm clock whenever you can.
Besides the duration of your sleep, there are a few other influences on the quality of your sleep. A few brief recommendations:
- Sleep in a dark room, or with a sleeping mask
- Only sleep (and do other bedroom activities) in your bedroom (don't use it for
study/work)
- Sleep in a quiet and safe environment
- Write your worries down before you go to bed
- Keep your bedroom clean and free of stuff that's just lying around
- Keep your bedroom cool (use a warm blanket if cold)
- Make sure your bedroom is well-ventilated