1. I prefer month to month in most instances, but CPM can be useful if the site offers potential traffic from visitors that I want.
2. CPM is generally what I use most.
3. You'll have to do your own research to find industry standards. My suggestion would be to start below industry averages in order to acquire initial advertisers, if you are launching a new advertising opportunity. Without historical trends for campaigns on your site, advertisers will be reluctant to initiate.
4. I would expect that hard-coded text links would have a slightly higher value for webmasters, so I would probably go with a higher fee for text links.