As a frequent return visitor, I can offer some suggestions.
First, arrive at least 30 minutes before your scheduled time. Also, they open the doors at 7am so, if you are scheduled for 8am you can avoid some of the opening rush and registration. They called me the day before and let me know that which was helpful. Most times they are ready to go with very little delay. I've tested mornings and afternoon. I prefer the morning. In the summer they are open until 10pm. The rest of the year 8pm. And, they are open 7 days a week.
They suggested that the easist way to find it is to GPS to "Boomer Jacks" in Bedford. When you arrive, there is a walkway to the right of Boomers and a two story clock tower. They are at the base of the tower on the left. In the morning, parking is not a problem but there is also parking behind the center except it's tricky to find the way from the front.
I have rarely had a bad experience with the staff. They are usually welcoming and patient. It is very important to carefully review the site information for the test you are taking and come prepared. The requirements are subject to change. Also make sure you have the correct Identification that conforms to the rules of the organization for which you are testing. There's little the staff can do if you don't have correct ID and name change and renewal/expiration. They will work with you but within limits. I've seen it happen. In Texas you can renew online, print out the renewal and bring it in with you. If your name changes due to marriage make sure you ID is changed too and it matches with your tesing organization through which you made the appointment.
The testing rooms are comfortable but if you prefer you can bring a sweater or light jacket. It should be easy to remove or put on. You can also bring ear plugs as long as they aren't connect by a wire. They have sound-deadening headsets and a headset with audio. I think the audio headset is more comfortable but now i use my own plugs.
Other than ID and any required paperwork, you shouldn't need to bring anything. They supply everything needed like paper and pencil and calculator.
If you want, you can bring food and beverage and place it in your locker. Some tests have different rules about locker access. I thought every test was the same but that's not the case. Pay attention to their instructions when you sign in at testing desk. Ask questions if you don't understand. There are a variety of tests with different rules. For example, access to phones and study notes are different.
I hope this is helpful. Testing is stressful enough without some sort of preliminaries.