One must avoid going on trips on Tisha Be-Av, because they divert one’s attention from mourning. One should also avoid friendly conversations, because they can lead to laughter and levity (SA 554:21). It is better to discuss the destruction of the Temple, Israel’s tribulations, and the ways of achieving repentance for both the community and the individual.

Even those who customarily visit cemeteries after reciting Kinot must take care not to go in large groups, because they might become distracted from mourning (Rema 559:10, MB ad loc. 41).

It is clear that one should not refrain from going to the Kotel (the Western Wall) out of concern that he might meet friends there and become happy. I heard from my father and teacher that there is no greater rectification for Tisha Be-Av than going to the Western Wall and praying for the Temple to be rebuilt speedily in our time. On the contrary, the fact that many people assemble there increases the power of one’s prayers and magnifies God’s glory. My father added that just as no one would claim that one may not build the Holy Temple during the Nine Days because it is an act of joyous building, so too it cannot be claimed that one may not visit the Western Wall on Tisha Be-Av since one might meet friends there. Rather, if one meets his friends there, he should avoid greeting them, but he may shake their hands affectionately and pray with them for the Temple to be rebuilt.