Tagging albums not in MusicBrainz

Hi,

I have a whole bunch of albums that are not to be found in MusicBrainz database. Fortunately most of the artists are there, but not some of their releases.

What is the best way to tag in Picard in order to get everything right? I have retagged almost all of my flac files with Picards help now and would like to get my collection as ordered as possibel.

-Stefan