Learn this list of ions. (Also available under Chemist’s Tools > Ions to Learn)

Cation: ammonium, NH4+
Anions: nitrate, NO3
acetate, C2H3O2
sulfate, SO42-
hydroxide, OH
phosphate, PO43-
carbonate, CO32-
cyanide, CN
chlorate, ClO3
permanganate, MnO4
chromate, CrO42-
dichromate, Cr2O72-

Hint: Make flash cards for learning the ions – on one side, write the formula, on the other side, write the name.