Agree with cp, map board on the bars is a very good idea, taking a map out of your pack for every decision is a massive faff. Boards are great, tough it seems to take some people some time to adapt to not being able to see the front wheel on techy downhills. Oh, and bear in mind that GPS are usually not allowed.
Aside from that, have fun. If it’s Trailquest/score format (pick your checkpoints) try and avoid climbing on singletrack. If it’s MTB-O/linear format, remember the shortest route isn’t always the fastest!