First, congratulations on thinking of entering a meet — you'll love it. It takes guts to get out on a platform and be judged by your peers and I admire anyone who does it. Second, just do it! You don't have to be an all-star the first time you go to a meet. The important thing is to get in one and see if you like it. No one's going to judge you as a person on how much weight you lift; and if they do, their opinions aren't worth a watery dump. Since you are new to this, let me offer a few points.
Open light in the squat.
No need to add fuel to the nervousness by attempting a weight you think you MIGHT get. The opening squat sets the whole tone of the meet for you: If you destroy it, your confidence is up, the butterflies will be gone, and you'll be awesome. You'll go back to your seat with a huge smile on your face. Of course, if you over-extend yourself too early, the opposite is true. In that case, prepare to have a long, miserable day.
Bring someone you trust.
This doesn't have to be anyone experienced in powerlifting meets but someone that will help you navigate the meet and help you through the day. It DOES help if this person has meet experience, but as long as you have someone that can handle you (wrap knees if necessary, get you water, check on flights, etc.), it takes a whole lot off your plate. You can just concentrate on lifting weight. Also, make sure you and your crew come prepared; pack your own bag and make sure you have everything you need. You shouldn't be running around borrowing a bunch of stuff from other people. And be wary of taking too many stimulants; it's a long day.
Don't cut weight.
Just weigh what you weigh. Worry about your training for the meet; no need to add cutting weight to your list of worries. Not cutting weight is a rule in my weight room. It's only for martyrs and victims.
Know the rules.
Every federation (at the time of this article about 458 in the U.S. alone) has different rules. Know the judging rules. Know the equipment rules. Don't be caught off guard. Ignorance is not an excuse. It's an embarrassment.
Ask other lifters and handlers at the meet for advice. 99% of the time people are going to be more than helpful. Just don't do it right before someone lifts. There's never a perfect time for entering your first powerlifting meet. You're never going to be strong enough; in this sport, the quest for a total shows that you can never be strong enough. Just go out there and do your best, and you'll have the respect of everyone in that room, no matter how strong you are.
As far as my training recommendations on how to prepare for either your first or your next meet, I wrote a whole book on it. You can get the hard copy or eBook and it will eliminate confusion and stress from your preparation. Either way sign up for the meet. It will give your training new meaning.