Every gal seems to have a different preference on how to do it, and even then some gals' preferences change over time. Some gals like light flicks of the tongue, others want you to literally chew on them.
Only about half the gals I see now enjoy it, or at least allow me to do it. There's only one that really gets off on it judging by the gyrations and liquid releases she exhibits.
In general, start out slowly and don't go for the clitoris right away, sneak up on it. Change up from tongue strokes to sucking once in a while, but not when you sense they are getting close. When they are getting close, then whatever you are doing to get them that far, stay with it till something happens.
Beyond that, it's uncharted territory.
By the way, doing a lot of DATY for long periods can be hell on your neck and shoulders. I have bone spurs in my shoulder as a result of one gal who used to insist I stay on the job for up to an hour each time we did it, and I was seeing her almost weekly for a period of several years. To prevent this kind of injury, have her lie face up with her legs over the side of the bed, and you kneel on a pillow on the floor facing her. That way your neck is not forced back with the resulting damage to the bones as the base of your neck.
I rarely do DATY as a result, and the pain has mostly abated, but if it were to continue, I'd need surgery to remove the bone spurs.