Create a "Repertoire" PGN. This file should contain only games played by strong players in the specific lines you intend to play. This turns a database of millions into a focused textbook of just a few hundred key positions.
Instead of having opening lines scattered across YouTube videos, Chessable courses, and notebooks, a PGN centralizes everything into a single, searchable file. build up your chess pgn
If you own the physical book, you can create a custom PGN for personal use: Book review | Yusupov's Build Up Your Chess Create a "Repertoire" PGN
Keep parenthesis nested neatly so your software reads the alternative lines without crashing. Instead of having opening lines scattered across YouTube
Open your chosen tool. Create a new database called Master_Full.pgn . Import every game you have. Even a bullet loss from 3 years ago is data for trends.