But for this last point, i will have to disagree. If you have already made an offer price, the seller will meet you base on your willingness to buy at that price. If you meet then disagree on price, that is a problem. e.g. i will only offer a price, if the buyer is willing to pay that price, then there is a reason to meet, if not will be wasting each other's time.
If you manage to do more homework after making an offer, and realise the offer price was too high, then call the seller and renegotiate, before meeting. If the seller is OK with the new price, then there is a reason to meet.