Repetition. Do the titration more than once, average out your results.
Know the weaknesses of the titration experiment, identify them and identify ways you could change these in the future (i.e. measuring accuracy, purity of the chemicals used).
Quality control, so are you keeping the chemicals separate? Using different pipettes for each chemical, or each strength (i.e. say you changed from 2 mol HCl to 5 mol, did you use a different pipette, clean beaker, etc??)