Trying to figure out the best way to use Nuget in a development environment to manage our own libraries.
We want to standardize on Nuget way of doing things for our 3rd
I'd suggest you use separate network shares or feeds (similar to what myget.org supports in the cloud) for different scenarios. You could imagine creating a CI share, a QA share, a Releases share, ...
Make people working on the referenced library do CI builds that drop CI packages on the CI repository for instance, and have them picked up by other projects (who just need to do a simple update, could be automated through PowerShell in pre-build: check for new version, if so, update).
Just make sure that when products release their milestones, they also release with released dependencies (could be as simple as switching feeds, releases will always have a higher version number than CI builds).
Hope that helps! Cheers, Xavier