Do what I did for my first comp this weekend. Take the plunge with a few friends split the cost.
Research, research, research on youtube and the forums about items and techniques people are using. I researched what most teams admit to using for injections, brines, rubs, and sauces. I also researched how to make turn in boxes, and presentation techniques. Then I practiced every weekend I could. Practice entailed, knowing when to wrap (by color) getting texture of the meat right, building parsley boxes, and making your presentation look good. I didn't necessarly always use the same rubs or sauces, I was more focused on technique and presentation, since I already had decided what flavor profiles I was going to use.
Also have a practice cook where you setup your cook site completely up. Whenever you have to go into the house to get something, write it down on your checklist. Keep a timeline of your cook. When I did my practice cook, I adjusted the timeline for turn-ins to start at 5pm. This allowed me to start my cook at 5am so I wouldn't cook overnight. This will allow you to practice your timeline to the T. In that practice also build your presentation boxes. Treat it like you would treat a competition. We also used it as a fundraiser. Family, friends, and neighbors came over and ate the bbq. We had a boot setup for donation and they filled the boot. We raised $450 in donations which offset some of the costs of competing.
Then just go for it. Get to the competition and make sure you drink lots of water, have lots of fun, and enjoy the experience. Go in trying to put out your best food you have ever cooked, but do not get mad of be dissapointed with where you place. My goal for my first comp was to not finish last in any category or overall. I finished 16th out of 43 overall, and didn't finish last in any category, so I exceeded my goals! You will meet some of the friendliest and most helpful people ever out there. It is a great experience, you will leave there completely exhausted and ready to do it again.