Grammar auction 	

1	I had to translate every sentence for my parents who couldn't speak English. 

2	Before I'd had breakfast I had a shower. 

3	I had confirmed the details with your office before I booked the tour.

4	Over the past month I had called your office three times on the phone to complain. 

5	I had graduated from high school several years ago. 

6	I had quit my job at the beginning of this year. 

7	Just after I  finished primary school, we moved house. 

8	When she was young, she had thought of a career in law. 

9	If you'd let me know earlier, I could have come. 

10	She had gone to many places, such as Europe, Canada and Japan as she likes traveling very much. 

11	He had a strange experience, which had happened while he was on holiday in England. 

12	When we'd finished eating, the boss made a speech. 

Corrections and notes

2	Before I had breakfast I had a shower. 

3	I confirmed the details with your office before I booked the tour.*
 
4	Over the past month I have called your office three times on the phone to complain. 

5	I  graduated from high school several years ago. 

6	I quit my job at the beginning of this year. 
 
8	When she was young, she thought of a career in law. 

10	She has been to many places, such as Europe, Canada and Japan as she likes traveling very much. 

11	He had a strange experience, which happened while he was on holiday in England. 

12	When we'd finished eating, the boss made a speech.**

Notes

* 3	I confirmed / had confirmed the details with your office before I booked the tour.*
The use of  'before' makes it quite clear that 'confirmed the details' is before 'booked the tour', so past perfect is not really necessary although it might be used for emphasis.

** 12  When we finished eating, the boss made a speech'  (Past simple)
This would also be possible here. The past perfect only emphasizes that the action was finished. But as the verb is 'finish', this is already clear.

These examples show that  you will hear and see slight variations to the 'rules' as you understand them.

Tip:
When speaking or writing, bear in mind that students frequently overuse the past perfect. Ask yourself whether the past perfect is necessary to make the times clear. If not, use the past simple.