So, you want to add custom ringtones, alarms and notification sounds to your Android phone without a third party application? Easy.

The Procedure

1. Plug your phone into your computer, and mount the SD Card as USB storage. 

2. Navigate to the SDCard from your computer (My Computer > Drive if you're on Windows / icon will appear on your desktop on Linux/Mac).

3. Once you're browsing the root directory of the SD card, you’ll need to create some folders for the media. So, in root, create the following folder:

media

4. Inside media, create another folder:

audio

5. Then, inside audio, create three additional folders:

ringtones

notifications

alarms

I think it's pretty self-explanatory as to where you place ringtones, etc, but to avoid any confusion; any sounds you want to use as alarms must be saved to the alarms folder.

Couldn't be simpler!