A lot of concepts in chemistry can be really confusing and difficult to effectively communicate, so it is extremely important that you pay attention during lectures because the more confident you are on a topic the better you will be able to explain it.
Give the students tips on how you studied and gained knowledge throughout the class. Additionally you can provide resources and activities to better engage with them.
Having additional resources (videos, websites, etc) for students that are struggling is really helpful. Most importantly, if you don't know something, ask the teacher! Your teacher doesn't expect you to know everything, so its best to reach out to for help to explain something to students if you aren't sure how to. It's better to ask than to teach the students incorrectly!
It is important to stay up to date on class concepts so you can be helpful. I like to listen to lectures and answer the questions in my own head. They also appreciate help and guidence on labs.
Something that really helps when you are mentoring is to act like you are just another student in the class. Learn and understand the lesson along with the students, take notes, and jot down ideas so you have as many answers as possible for the students. That way you 100% know you are as prepared as you can be.