Going current is easy. Make sure you read:
http://www.openbsd.org/faq/current.html
For changes you should be aware of, and be sure to run
sysmerge -s http://<your.mirror>/pub/OpenBSD/snapshots/<arch>/etcXX.tgz
and then once that's complete, run:
pkg_add -u
That'll ensure everything is in order as long as you grab everything from the same mirror.