Most agencies here seem to offer classes for interested people. I have several friends who have adopted and nearly all of them were strongly encouraged to do the following:
1) qualify to become foster parents. (Some states and I'm pretty sure DC have longish waits before birth parents can fully relinquish rights so this can help newborn adopters bring baby home sooner. Also, those adopting toddlers and older kids may be able to foster before the child is fully available for adoption)
2) research what would be required of your finances time, energy, social network (Is Grandpa racist?), etc if you would are willing to parent a child of a different race, an older child, a child with special needs, or a sibling group. Be honest with each other and with your adoption specialist.
3) find a family therapist specializing in adoption. I know a couple seeing the same therapist for nearly a decade (3 failed adoptions, followed by a transnational adoption and an open infant adoption, post adoption RAD issues, and navigating open adoption issues). They praise her through the roof.