"Really pay attention to me!"
qIm ("pay attention, concentrate") is commonly regarded as less exclusive, while buS ("concentrate on, focus on, think only about") suggests that you have a more singular focus. I can pay attention to an audiobook while doing something else, but I'm not really focused on it, or thinking only about that.
However, in this case, both HIbuS! and HIbuSqu'! seem like appropriate translations, so I've added them as accepted answers.
I also thought that qIm is intransitive (does not take an object) while buS is transitive (takes an object). So you would say jIqIm as compared to tlhIngan Hol mu'tay' vIbuS.
Please check with the other contributors if they want to include buS as an accepted alternative here because they might not want people using it when it does not have an object. I don't know myself for sure about it but that is just what I have been taught before.
I can see why you'd think that - the gloss "pay attention, concentrate" does sort of imply it - but we have canon which shows that both can take objects.
From Star Trek V:
loDHom jIHDI' qIrq qun vIqImchoH.
- "I've followed his history since I was a boy.
- "Track her course!"
qeylISvaD jach 'ej beyDaj luqImmo' / yuQDaq ghaHtaHbogh Hoch tlhIngan'e'
- Fore every Klingon on the planet / Followed her cry for Kahless.
We also have examples of buS being used seemingly intransitively, but then it's been translated as "concentrate", rather than "pay attention".