One of the most important things is to get the appropriate toothbrush, ie. one that says "soft". Not "hard" or even "medium", because while those feel like they would be more effective, they are much too harsh on the gums even the enamel, over time. They also force you to apply a lot of pressure if you want to clean between the teeth, adding to the damage.

A soft toothbrush using in small circular motions is best. And for the love of all that is holy, floss!