First of all, I should say that my experience was that of an eighteen-year-old girl with a much older man, which makes my experience different than others and specific to me, but I think my advice will be helpful to anyone considering having oral sex for the first time.
The first time I gave a blowjob, I felt like a rock star, a porn star, and a princess all rolled into one. Although it was my first time, I had practiced and studied for it like an SAT. I had read Oral Sex For Couples - The Art of Cunnilingus and Fellatio and Guide to Licking and Sucking - How to Impress Him with the Best BlowJob - The Best Illustrated Guide to Oral Sex. I took notes. I made index cards. I copied diagrams and committed them to memory. If I could get a five on the AP Literature test, it had seemed to me, I could teach myself to suck a cock.
Along with my book learning, I had also created "labs" for myself. I had tentatively explored with bananas and cucumbers, mimicking the diagrams in the books, and watching myself lick and suckle them in the bathroom mirror. I had touched the back of my throat with the handle of my toothbrush every single night for two months to diminish my gag reflex. At first, I nearly retched, but I made slow but steady progress, and it got easier and easier, but I had to be committed, tapping my tonsils with the intensity and single-minded focus an Olympic gymnast practicing backflips. After sixty straight days, I had been able to drop the whole length of the handle down my throat, and I felt I was ready to swallow swords.
Or rather, one sword in particular. Since I had met the man, for whom I was preparing, online, and based on our extensive cam sex, I knew exactly how big he was (6.1 inches long, 5.1 in girth/circumference) and I knew its peculiar shape and curve. With empty toilet paper rolls, electrical tape, duct tape, cotton balls, foam weather stripping, and a ten-inch beeswax candle, I had fashioned a perfect facsimile of his cock. First I had warmed the shaft of the candle to give it the perfect bend. Around the narrow candle, I had wrapped rings of the quarter-inch foam tape, giving it spongey-fleshy thickness. I had cut and spliced the toilet paper tube to an exact 5.1-inch girth (or rather just a millimeter thicker) to act as a guide. I had used cotton balls to sculpt a head, and then I wrapped the tube in duct tape. Lastly, I had used black and yellow electrical tape to give it black and yellow stripes like a bumblebee.
With my bumblebee in hand, I had knelt down naked (to set the mood) in front of my bedroom mirror, and watched myself stroke and suck, mimicking the extra research I had gathered on pornhub, (at this point I was just working on visual presentation) and taught myself to deepthroat like a porn star.