Vocabulary is the fuel, but grammar is the engine. Minna no Nihongo has a "Translation & Grammar Notes" book (Yellow/Green cover). Always study your Lesson 1 PDF vocabulary first, then open the Grammar book to see how those words fit into sentences.
Most PDFs are formatted in tables. You can copy-paste this table into a spreadsheet and import it into (a free flashcard app). Anki will algorithmically show you the words right before you forget them. This is the most scientific way to retain Lessons 1-25. Minna No Nihongo Lesson 1 To 25 Vocabulary Pdf
Studying from a consolidated PDF offers several advantages over just using the textbook: Vocabulary is the fuel, but grammar is the engine