Office365 Hints

"How do I change the default domain?"
Click your Company name in the upper left. http://onlinehelp.microsoft.com/en-us/office365-enterprises/7aad2c2e-72ad-43cd-8efa-a241cc4cdc05#bkmk_default

"How do I stop a domain from handling email through office365? I'm getting NDR's!"
Make sure the domain is changed from "Hosted" to "Shared". http://support.microsoft.com/kb/2510049

"How do I change the UserPrincipalName on an Active Directory Sync environment?
Set-MSOLUserPrincipalName -UserPrincipalName badlyspelledname@mydomain.com -NewUserPrincipalName correctname@mydomain.com http://community.office365.com/en-us/forums/160/t/13854.aspx

"How do I change the UserPrincipalName (email domain) in an Active Directory Sync environment?
In the on-premises Active Directory Users and Computers you can change the UPN suffix for those synced users. http://support.microsoft.com/kb/2523192

"I changed my password/username for the global administrator of Office365, and now sync doesn't work."
Official response: Run Dirsync Config again. http://www.microsoft.com/online/help/en-us/helphowto/4a8ae818-5e4b-4438-a278-3de927ed5762.htm
"cheating" response: edit the credentials within miisclient for TargetWeb Services.

"How do I force a sync?"
Easiest: DirSyncConfigShell.psc1, Start-OnlineCoexistenceSync. http://onlinehelp.microsoft.com/en-us/office365-enterprises/ff652557.aspx

I *know* people are saying, "I don't recommend ILM/MIISCLIENT.EXE" and they're right to ward novices off, because you really can break your sync/delete data if you're not paying attention. But on the other hand, if you look at what miisclient.exe *does*, you're going to be able to see a lot more troubleshooting options that  may help advanced users take better control over what's synced, including syncing certain OUs, forcing a full sync (this can be dangerous, as it can mass delete lots of users, but maybe that might be what you want in a fresh install, especially if you synced your entire domain and only want certain OUs to be synced.)

miisclient is important to know for troubleshooting, and if you know what you're doing, it can be used to great benefit or it can cause great grief.

Disclaimer: I can't help you and fully disclaim all responsibility (Don't blame me) if you break something with miisclient, and Microsoft may not necessarily support your tinkering, either. Document any changes with screenshots before and after. IMO, it's no scarier a tool than ADSIEdit or regedit. Use with appropriate caution.