Setting up user profile synchronization seems to be one of the most tricky tasks in SharePoint 2010. I experienced this myself just recently.
The problem was that I started with the farm configuration wizard right after I first installed SharePoint 2010. This basically sets up everything for you, including a default user profile synchronization service and My Site host. Starting from there resulted in lots of issues. I could get SharePoint to work properly with my own newly created User Synchronization Service. Even after properly setting the service connectors.
So after a lot of head scratching I just started all over with two fresh web applications.
In this post I would like to share which documentation I used to set everything up and make it work:
This is probably one of the best guides out there to set up user profile synchronization: http://www.harbar.net/articles/sp2010ups.aspx
Follow it to the letter!
This post explains common issues with user profile synchronization: http://www.harbar.net/articles/sp2010ups2.aspx
This is a video I found explaining user profile synchronization: It’s way too high level though: http://www.microsoft.com/resources/technet/en-us/office/media/video/video.html?cid=stc&from=mscomoffice&VideoID=29d6d43b-3a9a-4e1c-97e4-3fa93ac0d810
This is the official “Configuring profile synchronization guide” from TechNet: http://technet.microsoft.com/en-us/library/ee721049(office.14).aspx#WebAppProc
This TechNet article had some info related to planning user profiles: http://technet.microsoft.com/en-us/library/ee721054.aspx
So hopefully this will help you get you on your way!