How can you tell which ionic compounds will react in an aqueous solution

1.  Determine if the ionic substances can break apart into ions.
 - e.g. CaCO3 isn't very soluble, do it can't dissolve and dissociate.  If it can't pop apart, no ions.
2.  Swap the partners for all the other ions that you can get from step 1.  You can skip pairings with the same charge - a + can't get close to another + to react.
3.  Use solubility, acid/base, and redox rules to see if anything will happen with the ions in solution.