I have read the postings from you and the replies to you and would like to make some suggestions. You have mentioned several times that you are concerned that you will mess it up. I can understand that you want to have your first intimate intercourse be as good as it can be. The act of sexual behavior is a learned skill. It can be learned by example such as watching others. It can be learned through trial and experimentation. I learned from many different kinds of experiences and having several relationships. I will assume that you have no experience beyond kissing and clothed cuddling.
The emotional closeness that you and your loved one share is the essential ingredient. Both of you have kindness and patience towards the other. With such a nurturing attitude you can build a strong relationship. If I have not addressed the emotional or spiritual side it is not because of any lack of understanding, but rather that you are already grounded there and need the step by step directions in how to approach physical sex.
Be comfortable and relaxed, there is no need to hurry, Set aside a time when there is no other thing that needs to be done, perhaps a weekend afternoon or evening. Set a cozy atmosphere. Candlelight, light perfume or incense. Music. You may feel nervous and excited, that is to be expected, and can heighten the experience. Touch. Use your hands to rub, stroke and caress. Do what feels good. Touch the face, back, legs, the entire body. Kiss and use your mouth. Suck on fingers, neck, chest. Go slow , take your time. Let the feelings of excitement build. Words and sounds. Say what you are thinking. Whisper into your lover's ear how much he means to you. Tell him what you are thinking about, where your hands and lips will go. Let his imagination build his anticipation. Tell him he looks good to you naked. Good enough to eat. Have fun, play. Laugh.
Learning how to do it. Take a class in massage. Learn to use your hands to caress his body and yours.
Books. I can suggest “The Joy of Sex” as a great introduction to someone who is just starting and to someone who wants to learn more. You may want to read it with him. What could be more fun than turning the pages until you both see something you like and then trying it. There is also “Sex for Dummies” written by Dr. Ruth Westheimer. I have not read it, however I use the Dummies series books for many other subjects as they are well written and great for newbies. The major book stores have a section for love and sex that you may want to check out. Magazine articles are ok, but they are very limited in what they can tell you because of their short length.
Movies. You can learn by watching movies of others having sex. However I would caution that there is no right way to do it, and not to get too caught up in the pyrotechnics of explosive sex that both Hollywood movies and porn movies use. Look for basic love making guides such as the Playboy “Making Love Series” “Real Couples” series or products from Adam and Eve such as “Taoist Sexuality”. These videos teach loving physical closeness and how to enhance it. Avoid the Wham Bang sex of commercial porn, for right now.
Go to an adult gift store for ideas and inspiration. Be aware that they can be overwhelming if you are trying to be the good girl. Talk to the sales person there for help with useful toys or videos. Listen to advice, yet stick with what feels most comfortable, you are the best judge of that.
Try not to measure your selves against others or your own expectations. The experience can be good, not so good, and every variation in between. When you do it “right” sex is wet and messy and exhilarating. By learning a few skills you can have a wonderful experience each time.