The log-adjacency-changes OSPF configuration command got improved (IOS documentation claims it's happened in release 12.1) with the detail command that logs every step of OSPF adjacency establishment (sample printout below). Great troubleshooting tool :)

%OSPF-5-ADJCHG: Process 1, Nbr 172.16.0.21 on Serial0/0/0.100 from DOWN to INIT, Received Hello
%OSPF-5-ADJCHG: Process 1, Nbr 172.16.0.21 on Serial0/0/0.100 from INIT to 2WAY, 2-Way Received
%OSPF-5-ADJCHG: Process 1, Nbr 172.16.0.21 on Serial0/0/0.100 from 2WAY to EXSTART, AdjOK?
%OSPF-5-ADJCHG: Process 1, Nbr 172.16.0.21 on Serial0/0/0.100 from EXSTART to EXCHANGE, Negotiation Done
%OSPF-5-ADJCHG: Process 1, Nbr 172.16.0.21 on Serial0/0/0.100 from EXCHANGE to LOADING, Exchange Done
%OSPF-5-ADJCHG: Process 1, Nbr 172.16.0.21 on Serial0/0/0.100 from LOADING to FULL, Loading Done