The best lovers I have been with were adept at giving encouragement and coaching during sex.
I imagine that most everyone enjoys knowing that they are pleasing their lover. Moans and groans are great for that, but they're not very specific. Try specific encouragements like “Yes! Yes! Right there,” “Fuck me, fuck me please,” and “I love how you do that.”
Giving coaching during sex is a higher level skill. Just as most people enjoy encouragement, most people don't enjoy criticism. “Yes, there,” will get better results than “No, not there.” I enjoy being directed and even dominated, so something like “Hold onto the headboard! If you let go, I'm going to stop,” can totally make my day. My partner and I went to a workshop called “Rough Sex For Nice People” last week, so we got a lot of useful ideas.
Simple directions are often best in the moment. Higher/lower, harder/softer work well. I'll never forget one of my lovers saying “I said harder, not faster!” Apparently, I have a tendency to be too gentle sometimes. I got the message.
Shouting or chanting my lovers’ names is a big one for me, but there is alway a split-second delay for me to check that I'm shouting the right name with the right person. “Baby” is usually safe. My great great-grandmother married a series of three men named Jake. My theory is that she didn't want to shout the wrong name, so she standardized.
Learning to be vocal during sex is one of the most liberating things I've learned since I started having sex as a gay woman. There is so much freedom in being comfortable with who I am, and so much personal power in giving voice to it.