For a list of actions or items, you must maintain parallel structure. To do this, use similar grammatical units. If the first item is a noun, then the following items must also be nouns; if the first item is a verb, then make the other items verbs as well (including different types of a verb).

For example: Yesterday, I ran, went swimming, and bought groceries.

Ran and bought groceries are both past tense; however, swimming is a gerund (even coupled with ‘went’).

To fix it, change the gerund into a past tense verb.

Yesterday, I ran, swam, and bought groceries.

Here’s another example: At the grocery store, I bought milk, bread, eggs, and then I threw chocolate bars in at the cash wrap.

The “I threw chocolate bars in at the cash wrap” is a verb clause while milk, bread, and eggs are nouns. To fix it, I have to either make them all the same or use a semi-colon to make the second phrase its own sentence.

At the grocery store, I bought milk, bread, eggs, and chocolate. OR: At the grocery store, I bought milk, bread, and eggs; then, at the cash wrap I threw in chocolate bars.