One of the most common mistakes I see when editing is the use of a list where the tense does not match before and after the comma (,) or colon (:).
The easiest way to decide whether you’ve been consistent in each part of your list is to read your sentence all the way through using only one item out of the list as the completion of the sentence. Each item in the list should create a complete sentence with the phrase that sets up the list independent of the other items given.
Ex: In the study, researchers found that children who went to school hungry: lacked focus, felt fatigued, struggled with following instructions, and acted out more frequently than children not experiencing hunger.
Notice in the example that the phrase leading in the list is in PAST TENSE. This means that all verbs used in list items must also be in PAST TENSE.
To verify the consistency of tense, you can choose any one list item read it as a complete sentence.
Ex: In the study, researchers found that children who went to school hungry struggled with following instructions.
Each list item should complete the sentence correctly in this way.
The same goes for lists set up with commas.
Ex: It’s easy to walk into the grocery store and leave with a box of cake mix, three tubs of icing, and fifty granola bars, but not the milk I went for.
Using just one item from the list, it’s still a sentence because it’s conjugated properly all the way through. And, finally, to check your sentence one last time, you should be able to remove the entire list–that’s everything after the first comma and before the last comma, and still have a complete sentence (subject and verb phrase). The example below displays both concepts.
Ex: It’s easy to walk into the grocery store and leave with a box of cake mix, but not the milk I went for.
That’s all for today. Thanks for reading. Leave any questions in the comments section!
Amanda Marsico
Editor, Proofreader, Red Ink Enthusiast™
Red Ink Enthusiast™ 
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