I've attached a spreadsheet image to show the way I work on scenery. The whole spreadsheet area is basically a Level 7 tile, the small squares are Level 12 tiles, and the intermediate-sized bold squares are level 10 tiles. The co-ordinates shown on the axes are for the SW corners of the Level 12 tiles.
My procedure is as follows:
1. Geoconvert the the whole spreadsheet area with Levels 9 & 11 using FSET resolution 4 (Virtual Earth).
2. Mark in blue all the Level 12 tiles that are completely sea. I do this by going to the AF2 "Location" tab, clicking on places around the coast and reading off the co-ordinates from there.
3. Geoconvert smaller areas (usually 4 x 5 = 20 small squares) with levels 12, 13, 14 & 15 using FSET resolution -1 (Virtual Earth). Before doing this I carefully check each area for clouds and colour casts by zooming in using the AF2 "Location" tab. Since I've already used Virtual Earth to geconvert the whole area, these defects will be defects in the VE images. Any Level 12 squares with defects are colour coded as shown. They will be geoconverted using Google Earth images (assuming the latter are better). For coastal tiles I use GIMP to colour in the white areas on the BMPs using a bluish-green sea colour, saving the images as TIFFs before geoconverting them.
Whatever area I geoconvert I always add 0.01 deg all round so that I'm absolutely sure of having tiles filling the whole area. This is necessary because the co-ordinates shown are only approximate (to 2 dp) so you need a little overlap to be sure. I always set geoconvert to reject masked tiles.
The letters "TA" etc are only relevant to cultivation in the UK using the Ordnance Survey. They mark the SW corners of the Ordnance Survey grid areas.