Whatever suits your needs is best. I have two 4Gig HDs in an A3000. These are some of the princles I tried to use.
I tried to keep all partions under 700MB so they can be backed up to CD.
I sized 3 of them 100MB to install different boot options, very flexible.
I avoid naming any of them "Work". Too many install scripts are poorly behaved with a partion named "Work".
Some applications (YAM, Spitfire, iBrowse, etc) are always creating new files that can fragment a drive. These always get their own partition to protect the more stable partitions.
In the case of iBrowse, I won't let it cache to a HD at all because it will eventually corrupt it. Those files are sent to the ram drive and are deleted when powered OFF. I've never suffered a corrupted HD since doing this.
I like having seperate partitions for APPS:, MyFiles: (music, photos, videos, etc), and Archives:.
Its nice to have an empty 700 Meg partition to organise files there before writing them to CD.
I've had better luck and performance running emulated OSes on a seperate HD.
Finally, with two equal HDs, I can backup one to the other.
Hope some of this was useful.
