Load your model/mesh. Select Unwrap UVW in the modifer list.
Click on edit, to lead the UVW window.
Admire the shitty default UVW.
Click on face in the UVW modifier menu.
Select some faces.
Then click Planar View. Note, its best to chose an axis when you use planar view, else use a set view points (front/side/top and click 'Averaged Normals'.
Now look back at the UVW window.
Arrange the faces you have edited.
Lets make the view clearer. Click on options > Advanced, and delsect the following:
Grab the back faces and repeat.
Then flip the selection so you can arrange it nicely.
The excess shows more faces need to be arranged.
Grab sections and arrange them accordingly, preferably annexing joined polygons. The purple lines tell you where parts are joined on the model.
TIP: Only unwrap one half of the model if you have a symmetrical mesh. you can then simply mirror the mesh, and both sides will use the same texture.