Detailed Install Docs
First and foremost, while still in Windows, error check and defrag your drive. This makes the repartitioning of the drive much smoother and safer, no matter if you are using Partition Magic, fips, DiskDrake, or anything else.
Next, any time you seriously alter the disk drive it is dangerous (and you will do that twice during the install, once while creating the new partition [which will alter the partition table] and once when you write the bootloader [which will write a new boot sector] ) so if you are the cautious type, back up your drive.
A less time consuming safety measure is to make a copy of the boot sector.
Then, although Linux finds and installs drivers right for hardware 99% of the time, a step that will save you grief later, should something not install right, is to go to Windows Device Manager and write down all "resource" information about all your hardware. This includes device names and drivers, irq and dma channels, ioport addresses, buffer sizes, etc., for your video card, sound card, network card, scsi cards, modems, disk drives, cdrom drives, cd burners, etc. This can come in handy.