The best way to protect your skin against sun is to avoid the sun. Avoid stepping outside when the sun is too intense. Morning and evening should be the preferred time of the day to go outside. Make sure to keep infants below 6 months away from the sun as their skin is more prone to harm from the sun.
If you have to go out while the sun is intense, wear long sleeve shirts, a cap or a hat, and glasses to protect your skin and eyes. Since UVA can make it through cloud cover and harm your skin, use proper sun protection even on cloudy days.
The right kind of sunscreen can effectively protect your skin againt damage from the sun. Use a sunscreen that contains compounds like zinc, titanium dioxide, avobenzone, mexoryl SX. All these compounds help the sunscreen provide protection from sun without being absorbed into the skin. Avoid sunscreens with Vitamin A and Oxybenzone (a synthetic form of estrogen) that can be harmful.
You shouldn't stay longer in the sun even with higher SPF with only one application. Instead of staying longer in the sun with single application of higher SPF, use SPF less than 50+ and make sure that you reapply it regularly throughout the day. SPF higher than 50+ can give you a false sense of protection.
Water and sweat reduce the effectiveness and longevity of your sunscreen while you are swimming or exercising in the sun. Use water resistant sunscreens for better protection when you are in the water or sweating.