Common recommended: 7-9 hours of sleeping at regular times
Note: Individual needs may vary. Stick to what you feel good and rested staying in a regular sleep schedule.
Sleep Tips
Avoid bright light and screen lights 1-2 hours before bedtime. Light suppresses melatonin production, and melatonin helps falling asleep and makes quality of sleep better.
Stop taking caffeine until late time, like 6 hours (really varies by individual) before bedtime.
I drink 1-2 cups of coffee in the morning and take only decaf in the afternoon.
Then I stop drinking coffee (including decaf) from late afternoon.
Avoid food close to bedtime, typically finishing at least 3-4 hours before bedtime is recommended.
Eating late may make you to feel tired in the next day because resources for recovery process is shared by digestion.
It may also cause gastroesophageal reflux disease.
Use your bed only for sleeping. Not for reading, working, etc in order not to train your brain to associate bed with working.
If you cannot fall asleep within 15 minutes, get up and read for 15-20 minutes under calm environment.
Keep your bedroom dark and quiet
If you are suffering from irregular schedule, try to fix the waking up time than sleeping time.
You may end up sleeping less for several days until you get adjusted to the new schedule, but that's okay.
If you have or think you may have any disease that causes sleep problems (e.g. sleep apnea), consult a doctor.