Just recently passed this exam, and I didn’t find it particular difficult.
You can find information about it here –>
http://www.microsoft.com/learning/en/us/exam.aspx?id=70-687
And it measures the following:
This exam measures your ability to accomplish the technical tasks listed below.The percentages indicate the relative weight of each major topic area on the exam.The higher the percentage, the more questions you are likely to see on that content area on the exam.
The information after “This objective may include but is not limited to” is intended to further define or scope the objective by describing the types of skills and topics that may be tested for the objective. However, it is not an exhaustive list of skills and topics that could be included on the exam for a given skill area. You may be tested on other skills and topics related to the objective that are not explicitly listed here.
Install and Upgrade to Windows 8 (14%)
- Evaluate hardware readiness and compatibility.
- This objective may include but is not limited to: determine whether 32 bit or 64 bit is appropriate; determine screen resolution; choose between an upgrade or a clean installation; determine which SKU to install
- Install Windows 8.
- This objective may include but is not limited to: install as Windows to Go; migrate from Windows XP or Windows Vista; upgrade from Windows 7 to Windows 8 or from one edition of Windows 8 to another edition of Windows 8; install VHD
- Migrate and configure user data.
- This objective may include but is not limited to: migrate user profiles; configure folder redirection; configure profiles
Configure Hardware and Applications (16%)
- Configure devices and device drivers.
- This objective may include but is not limited to: install, update, disable, and roll back drivers; resolve driver issues; configure driver settings
- Install and configure desktop applications.
- This objective may include but is not limited to: set compatibility mode; install and repair applications by using Windows Installer; configure default program settings; modify file associations; manage App-V applications
- Install and configure Windows Store applications.
- This objective may include but is not limited to: install, reinstall, and update Windows Store applications; restrict Windows Store content; add internal content (side loading); disable Windows Store
- Control access to local hardware and applications.
- This objective may include but is not limited to: configure AppLocker; configure access through Group Policy or local security policy; manage installation of removable devices
- Configure Internet Explorer.
- This objective may include but is not limited to: configure compatibility view; configure security settings; manage add-ons; configure websockets; configure Download Manager
- Configure Hyper-V.
- This objective may include but is not limited to: create and configure virtual machines; create and manage snapshots; create and configure virtual switches; create and configure virtual disks
Configure Network Connectivity (15%)
- Configure IP settings.
- This objective may include but is not limited to: configure name resolution; connect to a network; configure network locations; resolve connectivity issues
- Configure networking settings.
- This objective may include but is not limited to: connect to a wireless network; manage preferred wireless networks; configure network adapters; configure location-aware printing
- Configure and maintain network security.
- This objective may include but is not limited to: configure Windows Firewall; configure Windows Firewall with Advanced Security; configure connection security rules (IPSec); configure authenticated exceptions; configure network discovery; manage wireless security
- Configure remote management.
- This objective may include but is not limited to: choose the appropriate remote management tools; configure remote management settings; modify settings remotely by using MMCs or Windows PowerShell
Configure Access to Resources (14%)
- Configure shared resources.
- This objective may include but is not limited to: configure shared folder permissions; configure HomeGroup settings; configure file libraries; configure shared printers; set up and configure SkyDrive; configure Near Field Communication (NFC)
- Configure file and folder access.
- This objective may include but is not limited to: encrypt files and folders by using EFS; configure NTFS permissions; configure disk quotas; configure object access auditing
- Configure local security settings.
- This objective may include but is not limited to: configure local security policy; configure User Account Control (UAC) behavior; configure Secure Boot; configure SmartScreen filter
- Configure authentication and authorization.
- This objective may include but is not limited to: configure rights; manage credentials; manage certificates; configure smart cards; configure biometrics; configure picture password; configure PIN; set up and configure Windows Live ID
Configure Remote Access and Mobility (14%)
- Configure remote connections.
- This objective may include but is not limited to: configure remote authentication; configure Remote Desktop settings; establish VPN connections and authentication; enable VPN reconnect; manage broadband connections
- Configure mobility options.
- This objective may include but is not limited to: configure offline file policies; configure power policies; configure Windows to Go; configure sync options; configure WiFi direct
- Configure security for mobile devices.
- This objective may include but is not limited to: configure BitLocker and BitLocker To Go policies; configure startup key storage; configure remote wipe; configure location settings (GPS)
Monitor and Maintain Windows Clients (13%)
- Configure and manage updates.
- This objective may include but is not limited to: configure update settings; configure Windows Update policies; manage update history; roll back updates; update Windows Store applications
- Manage local storage.
- This objective may include but is not limited to: manage disk volumes; manage file system fragmentation; manage storage spaces
- Monitor system performance.
- This objective may include but is not limited to: configure and analyze event logs; configure event subscriptions; configure Task Manager; monitor system resources; optimize networking performance; optimize the desktop environment; configure indexing options
Configure Backup and Recovery Options (14%)
- Configure backup.
- This objective may include but is not limited to: create a system recovery disk; back up files, folders, and full system; schedule backups
- Configure system recovery options.
- This objective may include but is not limited to: configure system restore; determine when to choose last known good configuration; perform a complete restore; perform a driver rollback; perform a push button refresh or reset; configure startup settings
- Configure file recovery options.
- This objective may include but is not limited to: configure file restore points; restore previous versions of files and folders; configure File History
Now what I used for this exam wasn’t much. First of
1: Use Windows 8 as your primary OS for a while (or use it as your primary OS as default! 
2: Now a bit how OS deployment works
3: TechNet, TechNet and a bit more TechNet
The following URL’s were very useful
http://technet.microsoft.com/library/hh831833.aspx Windows ToGo
http://technet.microsoft.com/en-us/library/hh832026.aspx Windows 8 technologies
http://technet.microsoft.com/en-us/library/hh831713.aspx Bitlocker
http://technet.microsoft.com/en-us/library/hh831409.aspx Applocker
http://technet.microsoft.com/library/hh824947.aspx Windows 8 and ADK
This is not an in-depth exam, is more about configuring the basics of each function within Windows 8, the depth will come with the next exam which is the 688 (Which Is still in development)
http://www.microsoft.com/learning/en/us/certification/mcsa-windows-8.aspx