I have migrated to svn many repos from older stuff, like SCCS and VSS. Migration strategies are important, and to decide about them you need to answer a few questions.
First of all, ask yourself if git or DVCS is the best option for you, your project and your company. Just don't be led by hype. It may be that a centralized VCS like svn may be a better option. There are tools to make them perform as DVCS, like the plugins git-svn and bzr-svn.
Second, ask yourself how much of the project history is needed, if any is needed at all. That may save you lots of time, disk, chaos and entropy.
When migrating, it is very important to tidy up the repo. Purge unnecessary files, binaries, archives, branches, etc. I have seen people who use VCSs like a trashcan. Bad practices may sink the repository performance.
After migrating, make sure users know how to use the repo and that understand the basic VCS concepts, either generic or specific for the VCS of choice. Try to remove practices and concepts
from the older VCS. As you mentioned it, best practices are very important, and they are not easily found on literature.
There is more I could say, but I guess by now it's ok.