Tripod Head Buying Help?

[Run59]

I have decided to buy the Vanguard Alta PRO 284CT (Carbon Fiber) Tripod Legs. However, I am confused about matching the tripod to head specifications. I like a couple of Ball Heads from other companies. I have read manyt articles where the shooter used mixed match tripod/head setups. Here is my questions:

1. How do you know if the tripod/head will work together?
2. Are the attaching plates univeral?
3. Does the base diameter of the head need to match the diameter of the tripod central column top?
4. What should I look for?

Also any advise on a quailty Ball Head would be appreciated. I like the Giottos Pro Ball head MH-1301 or MH1311 but both have different base diameters,