前に, あとで, and てから
Different forms connect actions with 'before' and 'after.' Distinguish the time of the whole sentence from the order of the two actions.
Dictionary form before 前に
寝る前に歯を磨きます。 means 'I brush my teeth before going to bed.' Use the dictionary form 寝る before 前に. The earlier action is brushing, even though sleeping is written first.
Even for yesterday, say 昨日は寝る前に本を読みました。 ('Yesterday I read a book before going to bed'). 読みました places the event in the past; 寝る前に retains the relative order.
The ta-form before あとで
ご飯を食べたあとで散歩します。 means 'I will take a walk after eating.' 食べた marks the meal as completed before the walk. This form also works for a future plan that has not happened yet.
With a noun, add の: 会議のあとで (after the meeting) and 会議の前に (before the meeting). Learn noun + の separately from the verb patterns before 前に and あとで.
Make the sequence explicit with てから
手を洗ってから食べます。 means 'I will eat after washing my hands.' It explicitly places completion of the first action before the next. Add から to 洗って, the te-form of 洗う.
てから does not always mean that there is no time gap between the actions. It establishes the order; separate time expressions tell you whether the next action follows immediately or much later.
Check: For 'I studied before going to bed yesterday,' should you use 寝る前に or 寝た前に?
Show the answer and why
Use 昨日は寝る前に勉強しました。 The final verb is past, but the verb before 前に remains in the dictionary form.