I'm not Catholic, but the Catholic Encyclopedia does a good job of outlining the importance of the genealogies here.
There are several purposes for including the genealogies in Scripture, some theological, some merely cultural.
On the cultural side:
The Hebrews shared the predilection for genealogies which prevailed
among all the Semitic races. Among the Arabs, for instance, no
biography is complete without a long list of the hero's ancestors.
On the theological side:
The priests and Levites had to prove their
legal descent in order to fulfil the honourable and remunerative
functions of their respective offices. On returning from the
Babylonian Captivity several were excluded from the priestly class
because they could not prove their Levitical pedigree (Ezra 2:62;
Finally (and most importantly), the genealogies help to establish Jesus as the Messiah, since the Messiah was to come from the line of David.
As for how to use them from the Pulpit, use them as they were intended, and don't fall into the trap of making more of them than what they really are. It's very easy to take a few verses and read a whole lot of meaning into them that aren't there. Stick to the Word, and what it says, and you can avoid a whole lot of confusion.