Look for the helping verbs in the sentence. Helping verbs are typically: is, was, were, been.
Look to see if the past tense form of a verb is next to one of the helping verbs in the sample sentence above. Sometimes there could be an adverb separating the two (i.e., Jane was carelessly taken to the hospital.)
Replace "was taken" with the past tense form of the verb "take," which is "took." Removing the helping verb makes the sentence grammatically incorrect. Without its helper, the word "taken" becomes an irregular verb in the sentence. It must be changed to fit the tense of the sentence, which is in the past. Here's an example of the sentence with the change: Jane took to the hospital by Mom.
Determine which of the subjects is performing the action: Mom. Determine what action that subject is performing. Since the sentence should be in the past tense, determine what "Mom" did.
Place the person who is performing the action in the subject position of the sentence. Draw a line through the first word "Jane" and through the last word "Mom," and place "Mom" in the subject position.
Remove Jane from the subject position and place her in a position so that she receives the action from Mom. The sentence becomes: Mom took Jane to the hospital by.
Remove the preposition "by" at the end of the sentence. Without the word "Mom" after the preposition "by," the sentence would be grammatically incorrect, because there must be an object after a preposition. The sentence now reads: Mom took Jane to the hospital.
Recheck to see if you can insert the preposition "by" back into the sentence. If you can't, then your task is complete. The passive construction has been corrected.