"Want" is a non-continuous verb, so you should say, "I wanted to tell you something." http://esl.about.com/od/grammarintermediate/a/noncontinuous.htm

"I wanted" is correct.

They're both correct. "I was wanting..." is more colloquial.

Both the ways of saying it is correct

"I was wanting to tell you something" and "I wanted to tell you something" are both correct and natural. Yes, we can "break" the rule of static verbs in some contexts. We would need some context to help decide which one you'd need to use.