More than one SP has told me, "whoah, you've got some skills." Maybe it's just flattery, but pretending for a moment it's not, here are my tips:
1. You have to be 110% into it. It's has to be what you're dying to do.
2. Related to #1 above: don't keep it a secret that you're dying to do it and enjoying it intensely! Groan and moan and grind your pelvis into the bed while eating her out (but be careful when moaning/groaning to NOT blow any air into her vagina).
3. Still related to #1 above: be fully committed. if you've booked 60 minutes, then accept (and love) that DATY might be the only thing that happens for 60 minutes. Don't chase her orgasm with a singular focus - that's no fun. If you're starting to worry about how long it's taking, she will sense that, and then it becomes miserable for everyone.
4. You should love how she tastes - both on the outside and the inside. A lot of people are self-conscious about their private parts tasting/smelling bad - your body language and enthusiasm should make it clear that everything tastes and smells amazing.
5. Personally, I always massage her nipples during DATY. I start gentle and then experiment with getting massaging her nipples a little harder, always trying to carefully perceive if she likes that or doesn't.
6. Really try to keep your senses and perceptions open to what's working and what's not.
7. Sometimes I find it hard to believe that my partner's moans and writhing is authentic - but I would NEVER let her know that. Once or twice in my experience I am pretty sure the moans and writhing was fake at first. Only for the moaning to gradually change such that 15 minutes later it seemed authentic. If I said, "oh, you don't need to fake", or "are you faking?" that would have immediately been a huge mood killer for both of us. If a partner wants to fake, that is their own decision, and I respect their body autonomy to fake if they want to!