Past simple :verb+ed / irregular verb 2nd column -- walked
He walked to school every day
past perfect: had + past participle (voltooid deelwoord) -- had walked
He had walked to school every day before he got a car
Past perfect continuous: had been + ing -- had been walking
He had been walking to school every day for a year before he got a car
Exercises on all verb tenses: www.englishpage.com