Ever thought what would happen if you lost your precious mobile and all your contacts? Disaster (unless you have a Google account) so make sure you back it up. Here's one way:
Contacts App > Menu > Import/Export > Export to SD card
and save all the contacts in a .VCF file on SD card, that you can copy to your computer.
Then, it can be useful to use a VCF to CSV or VCF to Excel converter, like this one (Python needed), to be able to read the .VCF with a software like Excel.