While understanding the types of situations that require the preterite is helpful, it is even more useful to learn the specific vocabulary words and expressions that indicate the preterite is probably the appropriate tense to use in the sentence. The following are considered preterite indicators
because each will require the verb that follows it to be in the preterite tense. This list includes words that automatically require the past tense, and you can be certain the preterite is usually the correct past tense to use if the verb is used in front of or following one of these expressions.
There are other words that serve as preterite indicators only when the sentence is definitely in the past. Something else in the context of the sentence or a previous sentence must indicate that the sentence is in the past, otherwise these indicators may be used with other tenses. However, if you know you need a past tense and you're not sure which of the two, look for one of the following words to indicate that the preterite is the appropriate past tense.
If there's a blank line in front of the indicator, the verb you will be conjugating in the preterite will be in front of, rather than after, the indicator.