This was originally posted in the Building Maker Help Forum, but this
seems to be a much more appropriate place for it.
--
I've created about 50 models so far. (Edit: I now have 38 accepted
models) With the help of some of others people in this forum, I've
figured out a work flow that seems to work. I hope that new Building
Maker modelers reading this will avoid some frustrations. I'm assuming
that you have at least tried to build a model or two, so I will leave
out all of the "Getting Started" stuff which Google has already
produced anyway.

Once I have picked a location, and started Building Maker, the first
thing I do is go to VIEWER mode. I do this to have a look at the
terrain; I always start modeling at the lowest point on the building
footprint. Switching back to EDIT mode, I start with my first block at
the lowest part of the terrain.

TIP: Resist the temptation to CONSTRAIN as many points as you can. You
have many images at your disposal, so ensure that you use only the
best, most distinct spots to choose a constrained point.

TIP: Constrain the high points, but after you set the low points, i.e.
the points closest to the ground, RIGHT-CLICK on the point and REMOVE
CONSTRAINT.
Why? Easy -- to prevent your block from FLOATING above the terrain.
All of my rejected models had floating blocks; I couldn't figure out
how to fix that, but I think I have now.
After you have constrained some very high-quality points, switch back
over to VIEWER mode. Orbit around your block, ensuring that you
haven't got a floater or some other weird thing happen. Satisfied with
your model so far? Good. SAVE IT! Fill in the basic details, but don't
get too caught up in them. You can edit all of the information later
in the 3D Warehouse where you can find your models.

Place your next block, and go through the same process of choosing
only the sharpest points to constrain. Check your model in the VIEWER
a lot, and when you are done the next block and happy that everything
looks good, SAVE AGAIN.

TIP: Snapping -- I've found that the best way to SNAP a point to a
line or to another point is to do the snapping as the LAST part of
placing that block. Use your imagery to accurately place the block as
best you can, and THEN turn on SNAPPING mode. Navigate to the common
corners and edges, snapping them as you go. I recommend that you turn
off snapping when you aren't using it, otherwise your points will
always be looking for something to snap to.

Once your block is set, your points are snapped, switch to VIEWER
again, orbit and examine as usual. If everything checks out, SAVE YOUR
MODEL!

What happens if your model is suddenly floating several metres above
the ground? Do you swear at the Google Earth Plugin and curse the
Building Maker tool? Yeah, go ahead and do that. Get it out of your
system! :) Then when you have calmed down, you can switch back to
EDITOR mode and have a look at what is going on. I would bet that to
your eye, your model looks just fine. So why is it floating? It's
probably an issue of Building Maker and the Google Earth terrain
engine, but you can work around it. As was suggested in the forum by
another contributor, check all of your ground-level points. If any of
them are constrained, simply RIGHT-CLICK on the point, and REMOVE
CONSTRAINT. Go through your model in all image views, looking for
constrained ground-level points, and remove the constraint. You should
NOT have a WHITE dot at a point. White dotted points are constrained.
We don't want that right now. Okay, so you've checked your model in
several image viewpoints, and removed the constraint on a bunch of
points. Now what?

Go back to VIEWER mode, orbit your model, and check to see if it is
now sitting on the ground properly. I have found that just doing that
solves *most* of my floating block problems. If your model has its
feet back on the ground, SAVE your model, and return to EDIT mode
again.

Let's say you removed the constraints as I suggest, but your model is
still doing a hot air balloon impersonation? Well, there's something
else you can try. Remember how you initially surveyed the terrain of
your model before placing your first block? Go back to that corner,
find the ground level point, and move it as though you are trying to
shove it down into the ground. You may not have to move it much. Don't
overdo it either, as too much is as bad as too little. With your
bottom point now "deeper" into the terrain, RIGHT-CLICK and REMOVE
CONSTRAINT yet again. Switch over to VIEWER again, and look at your
model. In many cases, this will fix up the problem. If you pulled the
point too far down, your building may now appear to be several metres
too tall, so if moving that point caused the model to screw up, go
back and adjust it in EDIT mode. A bit of trial and error,
experimenting with one or two points like that should cure most of the
floating issues. Once your block is grounded again, SAVE YOUR
MODEL! :)

TIP: Details on rooftops -- When adding a little bit extra to pimp out
your model, you will often have to mess around with some smaller
blocks to display heating and air conditioning units, and perhaps
other small structures. What I suggest here is that you first SELECT
the block that owns the roof you are going to work on. With that block
selected, use the PLACE BLOCK ON TOP OF SELECTED tool. Place your
block, using the same principles as the ground-level block. In other
words, select only the clearest, best points, and don't constrain the
bottom points. Move the bottom points to where you think that they
should be, but REMOVE CONSTRAINT when you are done.

TIP: Constraint Restraint -- Again, as I have mentioned, you need to
be careful of setting constraint points in every single image view.
Constrain in a couple of views, but if you set a constrained point on
the corner of an air conditioning unit on a roof in every image view,
you will have a lot of trouble getting it "just right". If your block
is no longer orange, then Building Maker is happy that you constrained
some points in a few views. As you scan through other views, and if
your block looks fine, DON'T ADD MORE CONSTRAINED POINTS. You are
going to cause the "geo-engine" go nuts trying to calculate an exact
position. It's not necessary to do that. Have a look at your model in
the VIEWER and you'll find that it looks pretty darn good. When it
comes to constrained points, more is not necessarily better.

So, to summarize:
- Survey your terrain in the VIEWER before you start laying down
blocks.
- Start at the lowest point and place your first block there.
- Don't guess at points; always use well defined visible points to
constrain on your block(s). If you don't have enough good points of
view, load some more images until you find one that works.
- Check your model in the VIEWER often, and if everything looks fine,
SAVE YOUR MODEL.
- Use SNAPPING mode only when needed. Place your blocks as best you
can, then snap the coincidental points and then turn off snapping.
- Don't constrain every point you can see. It may not be necessary,
and you may find it frustrating to have to figure out why your model
is doing weird things.
- This is supposed to be fun, so if it's driving you nuts, then get
yourself a soothing cup of tea or turn on some of your favourite heavy
metal music. Don't sweat the small stuff!
- Do participate in the forums and ask lots of questions. Give as much
information as possible, and provide a link to your model in the 3D
Warehouse if necessary.
- Do offer suggestions on workflow, as well as any tricks or
workarounds you figure out.
- Do make lots of suggestions to Google on how to improve the tools.
- Celebrate when you get your first approved model accepted into
Google Earth!

Happy modeling!