those/these

Hi there

Could you please explain to me what's the difference in usage between 'those' and 'these' (I know they're plurals of 'that' and 'this'), but I'm getting confused when I should use which

examples:

Sonny has many qualities worth recognizing, and the purpose of this letter is to point out two of these/those qualities.

West African cotton farmers are among those[\b] hardest hit by government subsidized corporate agriculture.

As Katrina's flood waters recede, government contractors are flowing into the Gulf Coast and reaping billions of dollars in pre-bid, limited bid, and sometimes no-bid contracts. Many of these[/b] contractors and the men who award them are the same players who bungled the reconstruction of Iraq.

Is this another one of those[/b] suicide cults?

If that means focussing, in these[/b] pledge forums, only on those[/b] issues likely to gather the most support, then I respectfully suggest that this is precisely what we should do.

I will actively support those[/b] people who, on behalf of all of us, refuse to register for an ID card.

Many thanx
Sylvia