Make sure your Jeep is in good mechanical shape before you leave the pavement. Off highway trips will quickly help you find any old, worn out or questionable parts - as soon as your suspension starts to articulate, you engage 4lo, etc parts that were OK on the road may quickly let you down.
Have a plan and a map, and let someone know where you are headed. Take the time before you leave to make sure the trails you plan to use are on public land and legal.
Air down your tires to 15-20 psi - that puts more of the tire in contact with the dirt, improves traction, and reduces your impact on the trails since you won't be spinning your wheels as much.
Check with your local Jeep dealer or one of the many local clubs on the west side to see if any of them are offering a class or seminar on basic off highway skills - great way to get familiar with your Jeep's capabilities and yours, and learn some valuable insight from some more experienced four wheelers. I know the Sundowners in Kalamazoo usually have a class in the fall, Cheap Thrills Offroad and the Two Trackers are also over on that side of the state, wheeling with a club can be a great introduction to the Jeep addiction.