What are ways to prevent cracking on suspended concrete floors?

We install concrete main deck floors (so essentially suspended). So these floors are 3-4" concrete slabs on a floor truss system. We have seen a few issues with the concrete cracking and thus spider web cracking flooring (tile). Some say using concrete with higher PSI will help, some disagree. What can we do to avoid this cracking? Higher PSI? Less water mixed? Etc, etc. Thanks!