何回くらい行うかをたずねるときは、How often do または How often does のパターンで始めて、そのあとに文の残りを続けます。
How often + do / does
How often do you exercise?
How often does she visit?
How often do they play football?
やってみよう: ___ you go to the gym? (How often do / How often / How often are) 答え: How often do — このパターンでは、"How often" のあとに do が必要です：How often do you go? これがないと（"How often you go?"）、疑問文として成り立ちません。
do または does？
文のなかでは、普通の疑問文と同じように選びます。you, we, they には do を、he, she, it には does を使います。
How often do you cook?
How often does he cook?
How often do they cook?
Not "How often does you cook?" — say "How often do you cook?". you には do を使います。does は he, she, it のときにとっておきましょう。
やってみよう: How often ___ Amina visit her family? (does / do / is) 答え: does — Amina は1人の人（she）なので、このパターンでは does を使います：How often does Amina visit?（"do" は you/we/they のときに使います。）
頻度で答える
特定の曜日ではなく、何回あるかで答えます：every day, twice a week, usually, never。
How often do you exercise? Three times a week.
How often does she visit? Every weekend.
How often do they meet? Usually on Fridays.
Not "How often do you go? On Monday." — say "How often do you go? Every Monday.". "How often" は何回あるかをたずねているので、every Monday のような頻度を表すことばで答えます。
やってみよう: How often do you play tennis? Pick the natural answer. (Twice a week. / At the park. / Yes, I do.) 答え: Twice a week. — "How often" は何回あるかをたずねているので、頻度で答えます：Twice a week。"At the park" は場所を答える表現で、"Yes, I do" は Yes/No 疑問文に答える表現です。
is / are ではなく do / does を使う
動作（go, work, eat）についてたずねるときは、do / does を使います。ここでは is / are を使いません。
How often do you travel?
How often does he call?
How often do they visit?
Not "How often you travel?" — say "How often do you travel?". do を落とさないようにしましょう。travel のような動作を表すことばには、is / are ではなく do を使います。
やってみよう: How often ___ you eat out? (do / are / is) 答え: do — are を選んだ場合、How often のこのパターンでは使えません。eat のような動作を表すことばには do が必要です：How often do you eat out?
やってみよう: Ask Hiroshi about his habit. How often ___ he take the bus? (does / do / is) 答え: does — Hiroshi は1人の人（he）なので、does を使います：How often does he take the bus?（he/she/it → does。）