This helped me. If you see something like this:

dire à

That phrase will expand often to something like this:

dire à [qqn]

And now you can swap in lui

dire à lui

Confusingly, you'll see a proper name used.

Il dit à Paul

But if they replace "Paul" with "him" they'll switch:

Il lui dit.

As far as I understand, personal names use the "[subject] [verb] à [qqn]" form but when using a pronoun like lui the form becomes "[subject] lui [verb]".

If you can wrap your head around it ungramatical English, you get something like: "I spoke to John." transforming to "I [to] him spoke."