Observations on cock sucking
I personally dislike sucking cock, although I have done so a number of times as certain situations called for it.
If you find yourself in a position where you are expected to suck cock, here are my observations:
1. As other posters have said, don't sweat it. It doesn't make you gay and when it's over and you've moved on with your life, you don't have to spend any time thinking about it you don't want to. It's remarkably easy to put it to the back of your mind. It is definitely a whole hell of a lot easier to forget about than getting fucked in the ass.
2. I'm assuming you're not being expected to deep throat if you're doing it for the first time. I've sucked cock many times and I've never been able to do it, so I'm sure you're probably not going to either. That being said, try as much as possible to breathe through your mouth. This will seem counter-intuitive (and would be impossible if you were deep throating) however, one of the worst things about cocksucking is the smell and the taste. By breathing through your mouth more than your nose, you can avoid the smell and taste to some degree.
3. Probably the most frustrating thing about cocksucking is how monotonous it is. It can go on for a very long time. And the more bored you seem, the longer it will go on. It is in your best interests to act like you're really into it as this increases your chances of getting the guy off. Otherwise, he may let you go at it for 20-30 minutes which becomes very boring and will probably give you a sore throat the next day from where his cock pokes you at the back of your mouth.
You should really do your best to get the guy to cum (might be helpful to use your hands as well). If you just suck at it halfheartedly for a while, eventually the guy is going to want to cum and if you aren't getting the job done, the danger is that when he is ready to go for it, he just grabs you by the back of the head and fucks your face like it's a pussy for a minute or two until he cums. If you're into cocksucking maybe this sounds like a hot fantasy, but to me this is very uncomfortable, and only ends with the humiliation of another man cumming in your mouth.
The load will taste like an oyster, except warm. Salty and gooey. If you like oysters, maybe you'll like it, but I hate oysters and I hate having a guy cum in my mouth (if he'll go for it see if he would prefer to give you a cum facial). I have never swallowed a full load as I have always spit it out, but even if you spit it out you will definitely get the taste and probably end up eating at least a little bit of it.
My personal advice to get it over with as soon as possible is to:
A) Wear a very sexy outfit, like french maid or schoolgirl, or cheerleader, something that fills a fantasy for him
B) One of my tricks is to apply a fresh coat of lipstick right there in front of him, on my knees, before I take him in my mouth
C) Act like you're enjoying it - tell him how big it is, how delicious it looks, and in between sucking how much you're enjoying it.
Give the head a lot of attention with your tongue, and get a rhythm going with your hand to pull out most of his dick and give it a few hand pumps.
Hope that helps - good luck with it.