Experience and practice are the only requirements needed to give a sensual blow job and provide a man with the highest degree of pleasure possible. Get your man to sit on the edge of the sofa with his legs apart. Kneel in front of him and with your mouth fairly close and partly open, wank his cock ever so slowly so that the head just protrudes from his foreskin, occasionally rubbing your thumb over the part exposed head. Look into his eyes and tease him by licking your lips (a wet warm mouth is very erotic). It won't be long before you have a raging hard on in your hand so turn your attention to a different area to take his mind off cumming too soon.
Cup his balls gently with your free hand and let your fingers explore the underside scratching lightly with your fingernails and paying particular attention to the area just before his anus. Gently pull down his foreskin to expose the full head of his cock. Close your mouth around the head and tease it with your tongue, still looking into his eyes and observing any reactions. Using your tongue, lick softly along the entire underside of his now throbbing cock. As you suck and lick you will learn those areas that give him the greatest pleasure when your tongue is touching them. He should by now have provided you with several clues as to which areas are most pleasurable to him.
The most sensitive area for most men will be the ring (or corona) of the head where the foreskin is attached. (or was attached if he has been circumcised). By continued licking and sucking around this area with your tongue you are going to bring forth a geyser. If you are not skilled and you want to please him in a hurry I suggest that you get him off in this manner in order to become familiar at first hand with the nature and delight of his climax.