If you want to keep your hair down overnight then my main observation is that my hair is less frizzy when it is moisturised. My reason for this is because when the hair feels dry it rubs against the pillow a lot more rather than being silky and just falling on the pillow. This means conditioning is a must and/or using a moisturising leave in hair conditioner/ treatment.
Also, before I go to sleep I apply Moroccan oil to the ends of my hair, which I got from ‘Body Care’ which is a shop that sells products cheap. Moroccan oil is good for reducing dry hair. It can be purchased on Amazon here if there is not a Body Care shop near you.
Then I apply a finishing polish on my hair after the oil which is by ‘Percy & Reed’ which is available here. This product is designed to be applied after you have styled your hair, however, I have found that it’s waxy consistency keeps my ends from becoming frizzy overnight, after all this product is designed to keep hair in the same style.
Lastly, if you don’t have anywhere to be the next day or you’re washing your hair in the morning or just planning on having your hair up the next day, then the easiest option is to wear your hair in a bun overnight. It is damaging for dry hair especially to be subject to friction from the pillow because this encourages split ends further. So until you can make your hair feel moisturised I would advise this just to avoid further split ends.
Maybe you’re lucky enough to have long hair so when you take the bun out in the morning you have gorgeous waves/curls, however, my hair is too short and tends to have way too voluminous curls due to there not being enough hair to weigh the curls down a bit.
If, like me, you’re hair is a medium length and you still want to wear your hair down the next day then you could make a plait overnight which will create much more manageable waves.
I hope this advice helps!(: Let me know if you have any other methods!