How can I perform a clean install of Arch?

Basically I had another distro on my hard drive but I want to format it for complete use by Arch. I know how to set it up and such, it's just the formatting/partitioning part that I'm a little bit confused about (read the 3rd paragraph to know why).

I did this previously by simply using cfdisk and deleting all of the partitions on the drive and creating new ones, but does this actually remove all of the previous data that was stored on the drive?

The reason I'm unsure about this is because when I went to mkfs.ext4 on the root partition it said it was swap and prompted me do I want to use it anyway, does this mean it will overwrite the previous one (which previously that partition was swap before I deleted it and wrote new ones).