Having one TopPanorama, one or two MPU's, one or two TWS and a BottomPanorama is a good standard desktop setup. For mobile having a few ad placements live is a great way to start.
Panoramas could be placed depending on the design of the site in the top, in the middle and in the bottom.
MPU's stand for Mid Page Unit and is best placed in the middle of a page in scroll, for example in an article or in a forum.
TWS are great for sidebar units.
For mobile a good way to increase revenue is by having a 320x50 placement sticky (sticking to the screen when scrolling). The other formats are more cube-like and work well to appear in further scroll of the page.
Please see Holid.se/formats where we visualize some of the ad format placements.