If you have water showing up in your basement, you need to get it repaired as soon as possible. Water is inexorable, and it will get into little cracks and make them bigger, and it won't stop doing it. If you call a basement waterproofing contractor to come and look at your basement to try to stop the water from getting in, one of the things that they are going to do is start tracking down where the water might be coming from. That means that they are going to look at some external causes before they do anything. So, what are some of the causes that a contractor will look for?
One common cause of water getting into your basement is your gutters and downspouts. The downspouts can cause water to pour right down into the base of your house, into your basement and foundation. You might not see it when it isn't raining, since there generally isn't water coming down your downspouts if there isn't rain, but you can figure out where the water would end up by looking at where the downspout ends and looking around to see if there is anything like a hole under the downspout. The contractor may suggest that you put something like an extender on your downspout because that will allow the water to end up further from your basement or foundation.
When your house was built, the ground around it should've been graded so that there is a slight slope away from your house. That grading acts as a drainage feature. It will let the water drain away from your house and your basement. However, if the grade was put in incorrectly or if the dirt around your house wasn't properly compacted, then the grade can change so that it is flatter or even sloped toward your house. That will funnel water right into your foundation or your basement. The contractor can check out the grade, and if there is a problem, they can add soil around the foundation to create the correct grade and make sure that the water doesn't go down into your basement.
When you call a contractor to deal with the water coming into your basement, the first thing they are going to do is try to figure out where the water is coming from, because if the cause isn't found, it will be really difficult to make sure that the basement is waterproofed correctly.