1: Find Some Shade
My number one tip for shooting on a sunny day is to try and find a location that has some shaded areas. Whether that be a tree or a building, make sure you have the option to move into the shade if the sun is too harsh. Shooting in the shade will also help prevent the model from squinting in all of your images, which often happens when the model has to look into the sun when shooting.
The images below were both taken in the shade using nothing but natural light. The first image (left) was taken on a very sunny day at noon when the sun was at its brightest. I had planned to shoot at other areas of the beach but the sun was too bright. Instead, I decided to move the model into the shade cast by one of the beach houses. This allowed the lighting to be even across the entire model, meaning no unattractive shadows caused by the sun.
The image on the right was taken in similar lighting, the sun was very bright on this day too, so it meant that it was difficult to shoot on the pier as I had planned. Luckily I was able to find a nearby ferry shelter which was painted white. The small roof of the shelter blocked the sun from directly hitting the model, allowing me to fake soft winter lighting on a sunny summer day.