Recommend OS : Ubuntu 14.04(LTS) 64bit.
Download address: http://releases.ubuntu.com/14.04/  Install flow:

STEP1：Start to install

STEP2：Choose installation type

You should choose your installation type base-on your server or machine.I always choose?”Something else”because I like to customize the partitions.

STEP3：Disk partitioning

STEP4：If you choose “Something else” on above step,you should customize the partitions.
STEP5：Choose your timezone

STEP6：Choose your keyboard type

STEP7：Fill in your information

STEP8：Installing…

STEP9：Install finish

And the installation of Ubuntu is complete,please reboot your Ubuntu.