Apologies for the corny title.

I'm going to start with the following at least how I helped myself going from slow to fast, and from unenthusiastic to enthusiastic.

First, the age old important factor: Communication, do you actually enjoy giving blowjobs? If the answer is "Yeah but....." stop right here things like "Yeah but he ate me and I feel like I have to return the favor" are deeply mistaken

So now that we've got that out of the way, Lets start with the basics.

Deepthroating

Depends on your gag reflex, test the limits. The easiest way to do it is with food, i.e banana the moment I knew that I could practically eat half of the banana with one bite I knew I could handle big sizes (biggest being 7" from head to crotch)

Deepthroating isn't really necessary for a great blowjob however if you feel like you can take deeper, taste the waters, you'll need a patient man and an average to big size, my advice is to swallow as much as you can until the limit and keep it there for 2-3 minutes, if you feel like taking a bit more will make you puke then don't push, Imagine there's a hot potato on your mouth and you need it to cool off

Gagging:

What if you gag? So? Keep on gagging don't feel shamed, with all the exes and men I've been with including my now husband they all loved how I sound don't worry if it sounds "porn-ish" it's hot, my husband now knows my gag reflex is good so he tries to slam it deep every now and then to get these sounds out of me

Sensual

If you think you can't manage going fast, guess what? Slow and steady wins the race, lock eyes with your man, make sure you are enthusiastic and vocal, even the sounds that your lips make around his cock is really sexy, use dirty talk, moisturize as long as you can and keep pressuring that cockhead, that depends on the man, mine loves it when I move my tongue in circles around his dick while jerking his shaft with the other half

Important tip: I love my man's dick when his balls sag and is generally warm, I would recommend using some olive oil on your hands so they will traverse really well around the skin

Use Hands

From my experience men love a combination of both I always know his cockhead is sensitive so I'll target it with my mouth and use the hands where I can't go experiment with it.

Result?

A nice load on my face. :)

Don't rush it, have fun with it.