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, its 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 therefor I stopped doing it that extreme.
More realistic would be: get at least 7 hours* of sleep during 'work days'. Try to go to bed about the same time every 'work day'. In the weekends, try to keep to this schedule as much as possible. And lastly 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, some recommendations are:
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
Don't sleep with the heating turned on, keep your bedroom cool (take a big blanked if cold)
Make sure you have some sort of ventilation of fresh air while you're asleep.
*This is different for everyone, 7 hours is a good duration for most people. But you should experiment with this and find out what works for you