How to make your hair stay straight all day?

Wash your hair as you always do. Condition it to protect it from the straightening iron that you'll use later.
Towel dry your hair. 2. Massage about 1 tbsp. of straightening product.
You need to use a high quality anti frizz solution as well as a straitening solution.
I use aquaplane products and it seem to do the trick.

Pang 4EN 063

I suggest you to use the straightening iron if necessary. 
Ceramic flat irons are generally the most effective and least damaging to your hair. 
Take your hair in small chunks and run the straightening iron from the roots 
to the tips all around your head. When straightening hair, use a heat protection product to 
lessen the damage done to your hair. 
Make sure your hair is dry before attempting to straighten it to avoid damage.

Amolwan 050 3EN

I think I have to wach my hair everyday.
I always dry my hair, sometimes I ill put treatment serum on hair.
it can make your hair strongly and straight all day.

Kamonwan 048 4EN

Purchase shampooing and conditioning products that are specially formulated to create straight or sleek hair. Just about every inexpensive brand of hair washing products has a line of products for encouraging straight hair, including brands like Garnier and Pantene. Avoid harsh rubbing with your towel when drying your hair after a shower. Pat and squeeze your hair dry with your towel rather than ruffling or intensely rubbing your hair dry to prevent frizz from occurring. Apply a straightening mousse, gel, relaxing cream, or leave-in conditioner after taking a shower on wet hair. Choose an anti-frizz product containing silicone to help seal in your hair's natural moisture.

Belinda