Last year I struggled getting the students to learn the difference between independent and dependent variables. I have realized, if I can get them to think about them outside of a science experiment first, it is then easier to transfer the knowledge.
In this file you will receive everything to make an interactive notebook entry as shown in my picture that you can preview. I print the cards on colorful paper and have students match them, and place them on which side they think they should go and then we spend the class discussing which card is the dependent and which card is the independent. This takes a whole class period in most of my groups.
Additionally, I have created a work sheet with a simple experiment that they must read and find the independent and dependent variables. The worksheet also reviews skills like finding a conclusion and hypothesis.