You get nothing if you don't try.
You need to remember a couple of things,
Wait, it's hard to sell cars at the best of times, dreamers, tyre kickers, silly offers, test pilots etc, if it's been up for sale awhile and he's had nothing but dreamers offering green sheild stamps, he's ready for a serious offer.
Be forthright, phone, don't mess around on email with offers, chatting on the phone tells him you're in the market.
Know what it is you're buying, what's the guide price, service-cam belt every 36k, let him know you know these things, you need to convice him this is what it is and should be like, this is what it's worth.
If he's not wanting to move on the phone and it's local, veiw it, compliment the car, but also point stuff out, if he thinks you're ripping it apart he'll get defensive, dislike you and clam up.
If all this fails, wait some more, ring back in a week, if it's still there he might be coming around to your side, if it's gone, there's always another around the corner!