I was half asleep the first couple hours so I don't remember things clearly. But doors at the test center will open about an hour before the test and they will close the door before they hand out anything to you and when they close the door kiss your last six months goodbye. I was dropped off so I didn't have to park but overall parking seemed ok with maybe 5-10 minutes wait max.
Here's the most important thing:
1. BRING YOUR OWN FOOD! there's long line for food and they were junk foods (hot dog and such). Junk food isn't the best thing to eat before going back for another 3 hours.
2. DO NOT EAT A LOT! You are already tired and you don't want to overfeed yourself too much because you will feel sleepy. You don't want your body doing all the work burning the food.
Leave your belongings in the car or you can store it at another room that is supervised by securities. The rooms where you'll be taking the test will have bathroom and you can go to bathroom in the middle of test if necessary but you'll be wasting time.