ring tones- you can email them to your phone, download from the internet, or connect to your pc and drop and drag. To save a ring tone or picture just long press on it a choose download. It will be store on your sdcard in a download folder. You will then need to move them from the download folder to a folder named media (that you will make) and have sub folders named ring tones, notifiaction, and alarms.
Your Incredible will sync your facebook contacts once you sign in not to sure about twitter but guessing the same as FB.
Tips and tricks is a sticky thread on the top of the Incredible forum.
Welcome to AC