At my barn, you learn everything - not at once. I started at my barn as an adult rider, so I knew the basics about tacking up but I said to her it's been a while, so she watched and gave tips.
The first thing I did was she brought out the horse and I held out my hand for the horse to sniff it. Did basic petting and grooming. Then she showed me how to tack up. I did walk the horse up to the ring, but at our barn if they are younger and less experienced, the helper may walk the horse or have 2 lead lines on and both walk up.
I think a realistic expectation- even if you tacked and rode before0 is to expect assistance/ good supervision. Even if you know what to do- you don't know that particular horses habits. If you don't know how to tack up, they may show you, and then next time, expect assistance because you may not remember everything from being shown once. I am a believer of slow and steady wins the race- if you want assistance a few times then good supervision to make sure everything goes right, it will just ensure that when you do it on your own, you got the routine down pat.
As far as your first lesson- I'd go into it expecting your goal to be to just ride the horse very basic. Feel the horses movement at the walk. Discover how much pressure is needed for a response ( start out with the least amount of pressure) Remember, its not just you learning the horses habits, its the horse learning your riding as well. The horse may not be as responsive or may stop a lot in the beginning for a variety of reasons, but don't get mad, try to understand why.
As far as videos and books- just search for ways to bond with thehorse andtips about riding. Even if you watch videos that are above your level just for fun, it will give you the excitement of what you can work towards. Heck, I watched a video on how to do some top level dressage move that I a not even close to accomplishing...LOL.
One I would check into is the tellington touch-even though its not really going to help much with lessons but rather a tool to work with the horse. There are books and videos. I will warn you- even though I stand by the tellington touch through experience with working with my horse- watching the videos- and especially reading the books- it sounds funny and a bunch of bologna. you are prolly gonna doubt that it works and may even laugh at it- I did and still do. The funniest one is the python lift, but my horse didn't like her back legs touched and after working with her doing very basic python lifts aspects, I can touch her back legs and she is fine. When she is nervous, I do other tellington touch aspects to help calm her down. Its not the fix all, but I find it is a great tool to use. (What also helped with the back leg situation is gaining the horses trust, being calm with her and working with her to work through the problem- the TTouch itself wasn't the solution, but a tool to use to help)
One more important tip-the best way to gain experience with riding horses is to ride. You will give the horse the wrong signals or confusing signals. You will have trouble getting the horse to do something. You won't always get the horse to do something smoothly. But through trial and error- and understanding and learning the best way to communicate with the horse you are riding, you will gain the experience and learn how to ask the horse horse in the best way to do a specific task. It may take some time, but through every mistake you may make, as long as you learn from it, you will gain that experience needed to become a better rider.
Since I am already writing a novel:
when you check out the barns- check the atmosphere. Do you want a more busy place that is going to have more social interactions between people? or would you prefer a quieter place? How are th horses cared for? How do the instructors interact with the students? What impression do they give you after you take the tour? Perhaps you can ask to observe a lesson. You can even start out taking a lesson or 2 at both places and see which fits your liking the best.
Good luck and have fun!