Your parish should have a catechist inservice, and many dioceses also have inservice programs and training programs for catechists. Most offer and many require a certification that you work on over time.
Your DRE will give you the textbook and provide you with guidance. I know several people who enjoy Catechist Magazine (
www.catechist.com).
Do you have children of your own? Are you familiar with the developmental stage of the 8th grade crowd? How are you on discipline and classroom rules and establishing your authority? With 8th graders, that is going to be way more important than theology at first.
Think back to when you were in 8th grade, then factor in the internet and all of the inappropriate television most have been exposed to for far too long. Last year, one of my 7th graders, when asked for a favorite movie, exclaimed “The Hangover Part II”.
It’s an up hill battle, all the way. But this age is also fun because they are really able to think and start to question things, they like to discuss and ask the tough questions.
Oh, and by 8th grade they have also been exposed to a boat load of factually incorrect history and factually correct but morrally bereft sex education in their public school system. You will have to spend a good deal of time deprogramming them.