I can see a crack in the corner of my basement and when it rains a lot water comes in through it. Is there a best way to fix this myself?

What material is your foundation made with? How much is under ground?

The basement is poured concrete and about 7 feet is underground.

Patching from the inside will not produce the best fix. You'd have to chisel a V shaped groove into the crack with the wider base of the V in deepest. You can then pound in expanding hydrolic cement. There are sealing kits that work a bit better. How to Repair Foundation Cracks Using Polyurethane Foam Injection . Best way is to dig down outside to the footing. Clean the concrete and then seal using expoxy or urathane expanding foam.