To not splash when you're peeing you should stand as close as you can to the toilet or the urinal and aim your stream of pee slightly downwards and towards the side of the urinal wall or toilet bowl, instead of aiming the stream directly into the water.
You can also place a couple of sheets of toilet paper on the surface of the water and pee on that inside to help break the surface tension and reduce any splashing of the pee when peeing.
Getting as close as you can to the toilet bowl or urinal is important to prevent splashing when peeing.
The closer you are to the surface of the water in the toilet bowl or urinal, the shorter the distance your urine will have to fall, which reduces the chance of splashing of the pee when you do pee.
Aiming your stream of pee towards the side of the toilet bowl or urinal instead of directly into the center of the toilet bowl or urinal also helps.
Sitting down to pee can also prevent splashing as well and even some men sit down to pee but standing is also okay.
If using a urinal you can consider using an end urinal if available to reduce exposure to splash back of pee from others.