Dear Mr. Junk,
Thank you for posing this question. FINALLY, something I know a little bit about...well, ok ALOT about. A kneeling, sucking, guzzling Britannica on cocksucking and takin loads.
When you suck off your first dude to completion, it will probably be in your mouth. You will not be takin him down your throat, as that comes later, so to speak. To summarize what others are alluding to:
Taking your dude's load in your mouth is the final part of the cocksucking experience. The gettin hard, suckin, tonguing, licking and suckin some more all lead up to the BIG EVENT. His breathing hastens, he becomes more interactive, mebbe start talkin, calling on his Maker, his muscles tense, he starts thrusting, maybe grabbin your head, his nuts tighten up and he moans, yells out, cusses as he shoots. If, as you propose, this first time is with a very special guy, you are gettin way off on his pleasure and demonstrating, well, if not love, certainly a definite bonding and carrying the whole thing to a new, deeper level. Like dude, you are taking his DNA...woof! It shoots out warm, smooth, a bit salty....prolly feels like a lot more volume in your mouth than you figured. Viscosity, volume, taste vary, but trust me...it is SO good...your first.