What’s it like the first time? What should I expect? (Done)
The only thing I can tell you for sure is that your expectations are probably not accurate 
Many, perhaps most people find the temple ordinances somewhat strange and unfamiliar. This is a completely normal reaction, because the things we do there and the way we do them are foreign to us! I believe there are a few reasons for this, discussed more here.
In our normal Church meetings, we don’t have many formal rituals, things that have to be done in very specific ways. Yet in the Temple ordinances, we wear ritual clothing, perform ritual actions, and say ritual words. As long as you go in expecting the unfamiliar (and read a few of the things here), you should be just fine. Don’t worry if you don’t experience great epiphanies or deep spiritual insights the first time through. Most people, like you, are simply trying to keep up.
It’s also normal to be a little nervous, but there is absolutely nothing to worry about! The Temples have special sessions for people receiving their own endowment, and temple workers pay special attention to them. You will have a little piece of paper pinned to your clothes indicating you’re there for the first time (it usually says “own endowment”), and someone will be close to you at all times. That person is called your “escort,” typically a parent or close friend of the same gender so they can accompany you in the appropriate dressing room. Your escort wears a little tag that says “escort.”
Frequently, there will be a small meeting of people receiving their own endowment and their escorts before the endowment session in which someone from the Temple Presidency gives a brief introduction or answers questions. During the ordinances themselves, you don’t ever need to worry about doing or saying the wrong thing. A Temple worker will always be close enough to prompt you or help you with whatever you need. As Elder Monson is fond of saying, “when the time for decision arrives, the time for preparation is past.” Once you arrive at the Temple, the time for preparation is past! I’ve made suggestions above, and your Bishop or Stake President may have specific suggestions for you.
On the day you actually go to the Temple, you should be clean and neat in dress and appearance.
When you go to the Temple, you should wear your best clothing, as you do when you attend church. When you are inside the Temple, you exchange your clothing for the white clothing of the Temple. This change of clothing takes place in a dressing room, where you use a locker and a private dressing space. In the Temple, modesty is carefully maintained. As you put your clothing in the locker, you can leave all your worldly distractions behind. Dressed in white, you can feel a oneness and a sense of equality with others in the Temple, for everyone around you is similarly dressed.
…it is pleasing to the Lord when we bathe our bodies and put on clean clothing, however inexpensive the clothing may be. We should dress in such a way that we might comfortably attend a sacrament meeting or a gathering that is proper and dignified.”
-Elder Packer, The Holy Temple, 73.
Typically, you and your escort arrive at the Temple and present your Temple Recommends to the person at the front desk. At that point, if you have already purchased your own Temple clothing, you will go to the changing room. If not, it is possible in the larger Temples to rent the necessary clothing for a minimum charge that covers the laundering costs, usually a couple dollars for everything you need. Once you have the appropriate clothing, you might meet with someone in the Temple Presidency for some brief instruction and then go to the locker room, at which point your escort and a Temple worker will accompany you through your Temple ordinances.
What Exactly do We Do in the Temple?
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