Final answer:
To increase the attraction between oppositely charged objects, one should increase the magnitude of both the positive and negative charges. This enhances the electrostatic force between the objects, as laid out by Coulomb's law.
Step-by-step explanation:
To increase the attraction between oppositely charged objects, one would need to increase the magnitude of their charges. According to Coulomb's law, electrostatic force between two charges is directly proportional to the product of the magnitudes of the charges and inversely proportional to the square of the distance between their centers. Thus, increasing the positive charge on the positively charged object and increasing the negative charge on the negatively charged object would make them attract each other more. Conversely, decreasing either charge would lead to a weaker attraction, as would increasing the distance between the objects.
When a charged rod is brought near a neutral object, for example, it can induce a polarization in the object, with charges within the object rearranging so that there is a stronger attraction (opposite charges closer together and like charges further apart). Neutral objects too, particularly those made up of polar molecules that have a natural separation of charge, can be significantly affected when in the presence of charged objects due to the same principle of electrostatic interaction.