Conversation cannot be taught in a formal setting and definitely not from books! How did you learn 'conversation'? It is not taught in British schools!
Confidence comes with time and practice - remember how you used to get tongue-tied in French lessons?
Vocab also takes time - learn 5 new words a day could be useful but only if you need those words in your everyday life e.g. 'tyre, tube, puncture, patch, repair' but not 'biochemist, tintinnabulation, contour, security, condiment'. We can all see the link between the first group but what about the second? It's just random!
Murphy's Grammar - if your friend can speak to a reasonable level, Murphy's (or similar) is a useful reference. He possibly knows more grammar than the average Brit! If I were to ask you to give me a sentence about cycling using the third conditional, how many of you could (without resorting to any reference works)? Rigid Raider's friend probably could!
Conversation is a living and breathing entity, 'conversations' in text books are more like movie scripts! Try asking your boss for a day off, don't you run through, in your mind, what your boss may or may not say - if he says this that I say that but if he...'? In the book, it's all black and white! Did I practice these 'movie scripts' with my students? Yes but with a twist! The students were expecting "OK, we will go to the Mall." but got something related like " I went there yesterday, let's play football." - end of movie script!
I once spent about 10 minutes in one class greeting one student. The stock answer here to 'How are you?' is 'I am fine, thank you and how are you?' OK, she asked me a question and got the stock answer and so it went on - they never used the stock answer again!
As someone has already suggested - BBC World Service. also DVDs - documentaries and films - with subtitles switched off and talking books.
Amusing tale about Mrs Hippo (MA English - U of Wisconsin), first visit to England, sitting in my eldest daughter's lounge and me with a mug of tea in my hand - voice from the kitchen "Dad, tea's on the table." Mrs Hippo looked at me, then to the mug and said 'You've already got one!' Now we have tea every night apart from Sunday when we have dinner - we're posh in our house!