First of all, as the post above says, make a Windows Repair Disc, (that is if you don't have a Windows install DVD).
All partition creation, deletion and resizing of Windows Partitions MUST be done using Windows tools ONLY. All Linux Partitions MUST be managed using Linux tools, like GParted.
If you want to Shrink or resize Windows Partition then see THIS.
For Windows Backup you can have numerous tools to do so. If you ask me, I'd say use Macrium Reflect... you read its 'How to' HERE.
Partitions are very personal there are no hard rules. I Dual boot Ubuntu and Windows on one of my machine and heres how I have them partitioned on 1TB HDD:
The legacy BIOS has msdos partition table which only supports 4 Primary Partitions. If we need more we have to make the Fourth Partition as an EXTENDED Partition, which is a Primary Partition and acts as a container for LOGICAL Partitions. We can have up to 100 or more Logical Partitions within an Extended Partition. Laptops with pre-installed Windows can already have 4 Primary Partitions so be careful.. if you force a Fifth in Windows the HDD will turn into a Dynamic disk and won't work with Linux.
50GB Windows \C NTFS Primary [for Windows System files]
50GB Windows \D NTFS Primary [for my Windows specific Data + that to share with Ubuntu]
25GB Ubuntu EXT4 Primary [for Ubuntu System files]
All the remaining GB EXTENDED PARTITION
4GB SWAP Partition Logical
25GB Free Partition Logical [I usually have another version of Ubuntu installed here]
All the remaining GB DATA EXT4 Logical [to store all my DATA]
Dual Booting is always a good idea for a beginner. There are a lot of Windows Applications that don't have an easy alternative in Linux, or there may be applications or games you are 'used to' in Windows, which you may find hard to run in Linux. (Some Windows Applications can be installed and run in Linux using WINE. You can see HERE what applications can run in Linux).
Ubuntu 13.10 is due for release this month. I suggest you install it and familiarize yourself with it. You can install 14.04 when it is out.
EDIT: Installation Guides... (Search the web for more)
http://members.iinet.net.au/~herman546/p23.html [info here and the following is old but should give you an idea]
My two cents..