General issues are at iCloud and Outlook Problems and issues specific to Calendar sync are at Calendar Sync Issues. iCloud 2 users should check iCloud 2: What you need to know and iCloud default data files
When you create new contacts in Microsoft Outlook, the contacts may not be added to the iCloud contacts folder. Try clicking the Refresh button. If this doesn't work, you'll need to either move the Contacts or create them in the iCloud Contact folder. See Save and Move Contacts to the iCloud Folder Tutorial.
Don't use iCloud calendar, contact, or tasks sync for Exchange, Gmail, or Hotmail accounts.
Contacts Disappeared from Outlook
All of my contacts disappeared from Outlook. How do I get them back?
iCloud creates a new contacts folder in your profile and moves your contacts to it. You can view the iCloud contacts in Outlook.
Go to the Contacts navigation pane and select the "Contacts - iCloud" folder to view your contacts.
If you want your contacts in Outlook's default contacts folder, you'll need to drag them to it: select all and drag or use the Move to Folder command.
Sync Stops Working
When Contacts disappear from Outlook's iCloud contacts folder because syncing has stopped, close Outlook, open the iCloud control panel then sign out and sign back in.
Just deselecting Contacts (and Calendar) sync, clicking Apply, then re-enabling both may also work.
If the sync stopped working and the iCloud add-in is shown as disabled in File > Options > Trust Center > Add-ins. Select Disabled Add-ins from the menu next to Go button then click Go. Enable iCloud in the dialog.
Show iCloud Contacts First in the Address Book
When sending an e-mail, & hitting the "To" button, iCloud isn't the default. How do i make iCloud the default address book?
You can't make it the default contacts folder, but you can show it first when you open the address book or click the To button in a new message.
Click on the Address Book (on the Home ribbon or Standard toolbar) to open the Address Book. Click on it's Tools, Options. Choose iCloud from the dropdown. You can change the search order there too, if desired. This order is used for auto-resolution, when a name is not in the autocomplete list.
In Outlook 2010 and up, the dropdown is at the bottom (see screenshot below).
In Outlook 2007, it's at the top:
As an alternative, you can use a sync tool. Although How to sync Outlook (Exchange) with iCloud (in the Apple Forums) uses CodeTwo FolderSync with Exchange, it will work with non-Exchange accounts. FolderSync copies the items between two folders so the contents are identical and should only be used to sync folders that won't sync with the iDevices, otherwise you will have duplicates (or triplicates) on your devices as it does a 2-way sync.
While the sync tools can do one or two way sync, if you just want to save all newly created contacts to the icloud folder, you can use VBA top move them on save. See Save appointments to a non-default Outlook calendar folder for a code sample that works with Contacts.
Tools in the Spotlight
CompanionLink synchronizes Outlook data with phones and other supported desktop applications and web-based services (like Google). Companionlink supports all versions of Outlook, including Outlook 2013 32-bit and 64-bit, and Windows 10.
Automatically synchronize your Outlook calendar and contacts with Google or iCloud. Access Outlook calendar and contacts on your Android phone or iPhone/iPad.
CodeTwo FolderSync Addin is an Outlook add-in that enables synchronization of folders. The synchronization of data will always take place between selected folders and the user can choose several pairs of folders that need synchronizing. Freeware.
CodeTwo Sync for iCloud syncs Outlook folders with iCloud folders automatically synchronizes Outlook contacts, calendars and tasks with the iCloud data file in Outlook. CodeTwo Sync for iCloud will let you keep the iCloud and Outlook folders in sync, so you don't need to move or copy contacts and appointments between the default Outlook folders and iCloud folders. (Now Free)
Backup and synchronize your personal data (contacts, calendar, files, bookmarks, etc.)with your phone, tablet and computer
Your sync-software can sync only default folders of Outlook, but you need also subfolders and public folders? OLMixedFolders can synchronize any Microsoft Outlook subfolder or public folders with your Outlook default folders. It uses categories to keep in touch with the origin folder. It is possible to create elements for the linked folders directly on your mobile phone. After synchronization, the element goes to the specified folder.
Save and Move Contacts to the iCloud Folder
The following tutorial shows you how to use the Move to Folder command to move new contacts to a different contacts folder. This will also work with appointments.
On the open contact form, click Save then go to File menu and choose the Move to folder command. If you previously used the folder, it will be listed on the MRU, otherwise you will need to select the folder.
To make Move to folder easier to use (and remember!), you can customize the ribbon, adding the Move to folder command to the Home ribbon, placing it next to Save and close. Note: In Outlook 2007, you'll need to add the command to the Quick Access Toolbar as it doesn't have a ribbon.
More Outlook and iCloud articles at slipstick.com:
iCloud and Outlook Problems: Syncing Calendar
Outlook and iCloud 2: What you need to know
Outlook and iCloud Sync Issues
Outlook and iCloud: default data files
Save appointments to a non-default Outlook calendar folder