Specific Praise
Say the one thing a generic compliment structurally cannot.
General praise is nice and forgettable. It could have been said to anyone, and somewhere both of you know it.
A compliment lands in proportion to the proof that you were actually paying attention. Naming a specific choice someone made is that proof, in a way enthusiasm alone is not. It also tells them something they can use again, which is what separates praise from flattery.
Name the choice, not the trait
Not that they are thoughtful. That they rebuilt the second half after the objection, and it worked.
Say what it changed
The effect is the evidence. Without it you have described something rather than valued it.
Say it where it counts
In front of people whose opinion matters to them when it is genuinely public praise. Privately when it is something they might feel odd about.
Stop there
Do not add a request, and do not soften it with a criticism. Both turn the compliment into an introduction, and that is how it gets remembered.
Go deeper
What the paid version adds to this one.
How to notice things in the first place, which is the real bottleneck
How this changes with your boss, your team, and your peers
The written version, where tone does none of the work for you
Six real situations on camera, including two that go wrong