Unit Selection
In single player mode it's not possible to see each stage before starting the
combat, so do not be afraid to select a few weaker troops and lose deliberately to
get a solid idea of the layout. These units will help scout so that you can formulate
a strategy for taking out the opponents defenses.
Three Stars to get a three star standing for each and every goblin stage you are
going to have to destroy everything to get the most additional bonuses.
Defense vs. Offense?
While focusing using only one aspect is possible, a small amount of both is
suggested and will work better for you in the long term than choosing one or the
other.