Target them and move up to their face and zoom in (I have that mapped to alt+pgdown). If they target you and hold eye contact for 5 seconds it is the sign they want to start with some light erping.

Use modified emotes such as

/facepalm motion
/em nibbles <t>.

/handover motion
/em touches <t> gently.

Of course, hug them and embrace them. Even kidnap them and see if they go along. /smirk confidently if they look at you in shock. If they're into horseplay, let them start it - if so, do more puerile things like slapping. If they're a hopeless sap, you might find yourself turning around and going through the trouble of typing their full name to execute

/stagger motion
/em falls into %actualfullnamebecauseifyouuse<t>youwillturnaround%'s arms.

It really depends on the person. And yes I know what's happening; I heal! Gotta pay attention to the field and everything on it.