Tifa is a 20 year old Bar Hostess in the Sector 7 slums. She was trained in Martial Arts by a teacher named Zangan. She grew up in Nibelheim with Cloud and has strong feelings for him. Aside from being a Bar Hostess, she is one of the main people of the Resistance group, AVALANCHE. She also looks out after Barret's daughter, Marlene when Barret is out fighting Shinra.
Just like Barret, I didn't really use Tifa to0 much in the game except when I had to. She is a real good fighter and should be in the front or middle. Also try to put good attack Materia on her, that way, she's good all around. Her Limit Breaks are based on the slot machine system, meaning that you have to play a slot machine to see what type of moves she'll do. You can get hit, yeah, or miss. The higher the Limit Break, the more slots you get. You can get her Level Four Limit Break by playing some notes on the piano in her room at Nibelheim. You can only do this on the second or third disc, and you must have Tifa in your party. There are two ways to get the notes for the piano. You can either copy them down in Cloud's past, {examine the piano in the Shinra Mansion}, or you can look in my tips section in case you forgot to copy them down or your just to lazy to copy them period. Her Ultimate Weapon can be found at the Wall Market in Midgar after you parachute into it and defeat Hojo. You'll need to come in through the Sector 5 door though, which means you'll have to dig up the key at the Bone Village.{See tips}. Like all Ultimate Weapons, only put Master Materia in them, since they have no growth.