The single biggest problem in science is defining science it self. The main idea of science is that conclusions are made on the basis of empirical evidence. The evidence comes from experimentation and observation.
The basic process of science is often described in what is known as the Scientific Method. It needs to be noted that is a basic description not an absolute methodology, but it is a good basic description.
It starts with an observation made of some aspect of the universe followed by a tentative description is made, called a hypothesis that is consistent with what is observed.
This hypothesis is used to make predictions that are tested by way of experiments of further observations Modify or abandon the hypothesis as needed in the light of results.
Repeat steps the previous paragraph as many time as needed until there are no discrepancies between theory and experiment and/or observation.
There is more to science than this, but it makes a good basic description.