Care of the Normal Foreskin
There is one major rule here, and it is going to surprise you:
There is nothing you need to do in order to care for your foreskin. It's that simple.
A foreskin is a natural item, just like an eyelid. And the glans is a natural item, just like an eyeball. No-one ever washed his eyeball with special care, or washed under his eyelid. And, in just the same way, there is no need to wash under the foreskin, or to wash the glans carefully.
There are issues people have with smegma. My dictionary says "A sebaceous deposit found under the prepuce". Smegma is, of course, the white, cheesy appearance "stuff" that lurks under the foreskin. It acts as a lubricant, has been shown by research to be beneficial in reducing the already low incidence of penile cancer, and can sometimes smell a little ripe.
Usually the foreskin gets flushed out with urine at pee-time, so smegma doesn't accumulate. But, if you have any concerns, simply retract the foreskin while showering or bathing and flush the smegma away by hand.
You can injure your foreskin. Here you need to take a serious look at what is going on:
Injuries to the tip may lead to scar tissue formation and an "injury created phimosis". That needs to go to the medic fast before it turns into something that can only be resolved by circumcision.