Some useful keys I tend to always use;

Space bar - switches between selection modes: point, line, polygon. I tend to stay on polygon
/ - deselect current selection
- (as in minus key) - hide selection: this is useful to remove surfaces that you don't need to see, or if a surface is behind another.
\ - unhide all
Shift \ ( | pipe) - hide inverted: this shows what's been hidden, and hides what's visible. So switches hidden.
] - select all connected polygons
Shift a - fit selected polygon
Ctrl a - fit all
" (quote mark: Shift 2 on UK keyboards) - invert selected. So selects everything not selected, and deselects what you selected. This can be useful to quickly hide everything. Select a surface you want to work on, invert everything, and hit the hide key.

In the perspective viewport
Alt and L mouse - rotate around view: this rotates around a centre point of your current view, not the current selection
Ctrl Alt and L mouse - zoom in / out
Shift Alt and L mouse - Move view about

Modify tab
t - move the selection
y - rotate the selection
h - stretch selection
Shift h - size selection

You can also hold Ctrl before using a modifier, and constrain the movement to one direction.

You can select a modify mode, then hit n to bring up the numeric panel, and change something using values instead of moving the mouse.

If you're in a modify mode, hitting Space bar will get you out of it.

Texture related
q - Change surface: used to assign or create a surface
F5 - surface editor (this is probably where you'll need to look up some tutorials)

In the bottom right, you'll see 5 letters W, T, M, C, S. T is textures. If you select that, then the dropdown shows all the existing UV maps.

Each viewport has some dropdowns at the top that can be used to change a view. If you set one of the viewports to UV, then select a UV map from the dropdown in the bottom right of the screen, then the UV map will be shown in the viewport. You can also show the image for the UW map, so you can see how the textures are mapped.

Other stuff
i - information on the current selection: can be useful to find the surface that is assigned to the selection
w - statistics: you can use this to select different surfaces by their characteristics. For example, all polygons with a certain surface

At the top right, next to the name of the model there is a number, then some boxes, split diagonally. These are the layers. Everything is usually loaded into layer 1, unless the model is saved in layers. You can split an object to layers, by selecting some polygons, cutting them (Ctrl x), then selecting an empty layer, and pasting. You can then select individual layers, or Shift L mouse click to select multiple layers. If you click in the bottom half of the split layer box, it will show the layer as an outline.

Layers can sometimes be useful if you're working on smaller details.

end - collapse all layers to one layer. You'll need to do this before trying to convert to an EEO or it won't load in game properly, if at all.
home - delete a layer
insert - inserts a layer
F7 - shows the layers panel. Useful if you end up with a lot of layers, and you can name them as well. For my Blackhawk cockpit, I had 15 layers.


I hope that's some help.