First you need write out the balanced chemical equation. You will often be asked about iron(II) ions reacting with maganate(VII) ions or with dichromate ions, therefore it is easiest to learn these two equations of by heart instead of having to work them out each time. Then, use the volumes and concentrations that you've been given, as well as the equation moles = concentration x volume, to work out the moles of reactant 1 (make sure that you convert all volumes to dm3). Then you can look at the balanced equation and the ratio between reactant 1 and reactant 2 to find out how many moles of reactant 2 are needed to react completely with reactant 1. You should have been given the concentration or volume of reactant 2, and therefore should be able to rearrange moles = concentration x volume to work out either the missing concentration or missing volume of reactant 2. There are more complex methods for more complex titration questions, however they all start with writing out the balanced equation and working out the moles from the values that you have been given.