The obvious place to look is in places where water flows in wet weather. Many times you will be able to find pockets of standing or even flowing water.
If there is no water on the surface you may be able to dig in a low spot and hit water without too much effort.
I have never had to find fresh water on a beach, but I did read a survival manual written in the 40’s or 50’s that insisted that there was fresh water on almost every beach.
The instructions went something like this. Walk on the beach away from the water to the edge of the sand. Then dig down until you hit water. This according to the book is usually fresh water.
The theory is, rain water runs off and hits the sand and immediately sinks down to the level of the salt water. This builds up since it takes quite a while to become mixed with the salt water.
If you are in an area with no obvious places to look, keep an eye out for water loving plants like cattails, or willows. Cottonwood trees usually grow near water also.
If you can find a muddy, or wet looking area just dig down until you have water in your hole.
We’ve all seen how to make a solar still, but if you have somehow missed it. Dig a three foot wide and up to three foot deep hole. Place a container in the bottom and cover the top with plastic. Place a small stone in the center of the plastic to create a low spot.
When the sun hits the plastic it will heat up in the hole and cause water to evaporate, which in turn condenses on the plastic and drips into the container below the spot where you placed the stone.
Clear plastic bags can be tied to tree branches, and the sun will “cook” some water out of them. Slip the end of a leafy branch into the bag and tie the neck around the branch. It is a good idea to set up several of these if you plan on using it for your water supply.
As with most wild water sources it is always a good idea to treat your found water.
PS: Here's the resource I've put together to take a lot of the guesswork of this whole water sourcing and treatment during an emergency subjects