I usually only allow paragraphs to be indented when there's a need for them to be: only if the previous "element" could be confused and thus "merged" with the paragraph in question.
In practical terms, this means that there's no indentation after a
\bigskip, nor after
enumerate, nor after displayed math.
Now, when typesetting floats it's hard to enforce this style: I'd like to leave no indentation after a float (in my opinion, it's hard to confuse things here).
Given, a paragraph may well finish "flush" to the right margin and continue a new sentence just after the float...
The "solution" I'm looking for then would be to force floats to occur (as many as need to) inside paragraphs, so that the first letter after the float is a lowercase, non indented, letter.
PS: I usually also set
\setlength\parfillskip=2em plus 1 fil, so as to have a consistent "visual clue" that a paragraph is over.