Use an empty variable instead of ""
Uninitialized variables are set to a special value: empty. When empty is cast to a string it becomes "".
Contrived example (using z instead of ""):
For i=1To 5
For j=1To i
For numeric types Empty is 0, and for booleans it is false. This can cut down on initialization code.
a=inputbox("Enter Starting Value")
done=(b>10000 or i>10)
msgbox "Your "&a&" rabbit(s) have turned into "&b&" rabbit(s) in "&i&" years."