All problems can be categorized into four sections. They are either host system issues, configuration mistakes, network issues, or software bugs. For each type of problem, a different method of gathering information works best.
Most problems on the host itself become apparent when installing or starting Openswan. Openswan logs precise details of anything that goes wrong. If Openswan suddenly fails to start, check whether some automated update has changed something.
For example, a new kernel could have been installed that does not support KLIPS, where you had previously compiled KLIPS for the kernel. Perhaps someone changed a few firewall rules, some IP address on the host changed, or you are using a nexthop
value, and your ISP has changed your default gateway. These problems should all have very clear error messages in the log files, and should be very obvious, though fixing them might involve some work.
A more subtle error can be related to the host clock...