(no subject)

[gnomygnomy.livejournal.com]

I need help with a rule that's never been fully explained to me before concerning быть. It seems that when you follow the verb with a noun, the noun should be in instrumental case, such as:

Он хочет быть врачом.

But what if you follow it with an adjective?

Он хочет быть счастливым?

And what if you change the tense?

Он будет/был врачом/счастливым?

If these examples are correct, then when, if ever, is it not appropriate to follow быть with a noun/adjective in the instrumental? Or is this just one of those always-consistent rules that somehow missed me?

Thanks for your help, guys!