A swap partition (at least 32MB) — swap partitions are used to support virtual memory. In other words, data is written to a swap partition when there is not enough RAM to store the data your system is processing. The size of your swap partition should be equal to twice your computer's RAM, or 32MB, whichever amount is larger.
For example, if you have 1GB of RAM or less, your swap partition should be at least equal to the amount of RAM on your system, up to two times the RAM. For more than 1GB of RAM, 2GB of swap is recommended. Creating a large swap space partition will be especially helpful if you plan to upgrade your RAM at a later time.
A /boot partition (100MB) — the partition mounted on /boot contains the operating system kernel (which allows your system to boot Red Hat Linux), along with files used during the bootstrap process. Due to the limitations of most PC BIOSes, creating a small partition to hold these files is a good idea. For most users, a 100MB boot partition is sufficient.
A root partition (1.7-5.0GB) — this is where "/" (the root directory) will be located. In this setup, all files (except those stored in /boot) are on the root partition. A 1.7GB root partition will permit the equivalent of a personal desktop installation (with very little free space), while a 5.0GB root partition will let you install every package.