Scientists use the principle of Ockham's Razor as their guide. Ockham's Razor states that when there are multiple consistent theories are being considered, the choice should be the simplest one. Simple theories have an intuitive appeal, but that is not a justification of Ockham's Razor as a principle of reasoning. A justification should demonstrate that preferring the simplest compatible theory is better at finding the truth than any other competing strategy. 
This article does a good job with great cartoons of explaining why this principle is valid. Very insightful. Here's the link.
UppublishedAt: here is an animated older version. The link above goes to the version 2 story board which has not been animated.