Adding 3D elements
When importing your geometry make sure that the scale is right and adjust it if necessary. It may be a good idea to keep the ground plane as a reference when placing your objects to keep from intersect with it so keep the ground plane on a separate display layer.
With and without visible ground plane
Hint: Keep your scene organized by grouping and creating display layers.
Animation
fxphd.com graph editor intro video tutorial
Pixar animator Victor Navones' spline tutorial
A fantastic animation blog by Cameron Fielding at Disney
First make sure that playback speed (window-> settings/preferences->preferences->timeline) matches your recording speed (HD=30 fps, NTSC= 29.97 fps, PAL =25 fps)
With the image plane sequence as a guide start animating your 3D elements whether it is a city being hit by a meteor, a feather flying through the air or a totally reckless ladybug- inspired transport pod.
Make sure to spend time on the animation and polish it so that it is nice and clean. If possible, get some other peoples opinion and really try to nail the animation before moving on because it is very, VERY annoying and time consuming to have to do this over again(and we all know time is money :)
Render out simple playblasts to get a sense of how the final animation will look
Playblast animation test