You set a price high enough and make an offer to all the shareholders, who might or might not want to sell to you at that price. And then there are complex rules about how many of them have to accept and what happens to those who didn't want to sell.
There are usually shareholder agreements in place that not every single shareholder has to agree to a acquisition. Otherwise, you'd never be able to acquire a company if just one shareholder, holding one unit of stock said "no".
I think in most jurisdictions there is a law that enables a supermajority shareholder to take possession by a forced buy-out of remaining stock, at a "fair price". Thus a separate shareholder agreement is not necessarily required.
This comment makes no sense at all. Dole didn't offered anything! In case someone may be getting confused about the process: Murdock (who happened to be Dole's chairman and CEO) offered $12 in June (when the stock was trading at $10.20) for the shares he didn't control already. He raised his offer to $13.50 in August.
