Whist there’s certainly a value in developing tip-of-the-tongue responses there is also a danger that we just sound like slick but insincere sales people.  If the client gets the idea that the response is just a stock, scripted comeback they’re unlikely to be won over.  So try to ensure that wherever appropriate you show a genuine interest in their concern and ask good quality questions to investigate the issue further.  This can be tricky particularly when it’s an objection that you’ve heard hundreds of times in the past but if you investigate properly not only does this show empathy it also has the effect of making even a stock response sound as if it is tailored.