Divert and block the water from entering. :)

Pretty vague answer to a pretty vague question.

Work on landscaping and sealing the area around the perimeter of the basement first. You need at least a 3-4 foot perimeter that is designed to shed water and make it move away from the house. Allow the water to naturally flow away from the house.

Then analyze the water flow from the rest of the yard and figure out how to make it go around the house. For example, if the front of the yard is higher it probably makes the water run down toward the back. Install drain pipe, gravel drainage, and other structures in the ground so that the water seeping into the ground in the high areas has a path around the house to the low areas. How well this works will depend a lot on the type of soil.

If you have deep pockets, excavate around the basement walls and have them sealed, and then add drainage so that water will be routed around the basement walls.

Assuming you can divert most of the water from outside, you should now seal the basement walls with appropriate paint or sealer. It won't be 100% effective, but it helps a lot to stop moisture penetration. If you still get a lot of water penetration you may need to have french drains installed on the inside of the basement walls, with all the drains leading to a sump pump.

If you already have natural drainage to a low point under the basement floor, you may get by with just installing a sump pump at that location. However, it all depends on the water draining to the point where you install the pump.

I would start with all the outside work first, and then see how well it works. The least expensive solution is one that keeps that exterior moisture from even reaching your basement walls.

Bruce