I agree with all the advice about finding a man who will treat you right and you should definitely stick to only doing what you want to do sexually, but as you were after tips these would be mine ...
In my experience guys love enthusiasm (mine comes easily as I adore giving him head, he's always clean and it's now obvious when he's going to cum although he still likes to tell me)
Talk before about where he is allowed to cum or whether you would prefer it to just be foreplay before hopping on so you don't have to have the taste. (Some are vile and some are not so bad)
I love to do it on my knees and look up into their eyes! Eye contact is hot and you get to see how much they are really enjoying it!
Practice on your finger just so you can tell a little bit as to how it feels! If your mouth is already wet just slide a finger in slowly at first so you can imagine the different sensations and you can lick it from base to tip and then suck your finger harder, changing pace or keeping a steady pace!
My man loves me to lick him from base to tip and then swirl my tongue around the helmet, the most sensitive parts tend to be the frenulum and the bits either side. Sometimes the anticipation is hotter if you go really slowly, licking, kissing and nibbling as they love the sensation but can't wait for you to try to fit as much in as you can!
It makes a difference whether you go hands free and rely on you to keep sucking to keep it in your mouth while you're getting him hard or whether you use your hand to keep it steady and set your own pace but pretty much all is good! You can ask him where he likes it and where is most sensitive!
You can change it up by alternating between hot drinks and ice cold drinks as that feels amazing! I wouldn't recommend booze as that tends to sting!
Some guys love a gentle tug on their balls too, some guys love you to suck their balls or take a whole testicle in your mouth (some don't like it at all)
While you aren't confident at it then don't let them push your head or thrust at you, while your new to it then just remember that you're in charge and that you're the one giving the blowjob and they are lucky to receive it from you in the first place!
Never get bullied into doing something you hate xxx