Do a rough titration; meticulously perform three to five repetitions, taking utmost care when coming... closer to the rough reading.
Plot, excise outliers, draw a line of best fit; but I can't see that happening here, fall back on averaging.
Wash your glassware with substances that you'll fill them up with - don't use water, lest you mess the concentrations. That's validity.
Obviously, perfectly and chemically-pure standard solutions.
Other things:
*Stat analysis. This is best done if you've got many points, and is totally gratuitous for the purpose of HSC Chem, tbh.
*Sooomething about the equipment. I forget.
*To improve reliability, compare your results with your those of the rest of your class.