Every piece in shogi has a relative value. The general order from highest to lowest is:
Keeping these values in mind gives rise to an important concept: material gain (komadoku).
For example, suppose you trade your Knight for your opponent's Gold. Since Gold is worth more, you have gained material — your position has become objectively better. Similarly, if you trade one major piece for two Golds or Silvers, the player who receives the two pieces has made a significant material gain.
Accumulating material advantage leads directly to a better position. Simply asking yourself "is this trade good for me or bad for me?" before each exchange will meaningfully raise the quality of your moves.
Promoted pieces are the most powerful forces — never miss a chance to promote
When talking about piece values, promoted pieces deserve special attention. The Dragon (promoted Rook), Horse (promoted Bishop), and Tokin (promoted Pawn) are among the most powerful attacking pieces in shogi.
The Dragon and Horse keep all the movement of their original forms and gain the ability to move to adjacent squares as well, making them fearsome pieces that can dominate the board. The Tokin is often underestimated — "it's just a promoted Pawn" — but this is a serious mistake. A Tokin moves like a Gold general, and because Pawns are plentiful and easy to advance, you can create multiple Tokin and pour them into the enemy camp one after another. For your opponent, a Tokin can be every bit as dangerous and annoying as a Rook or Bishop — it is a top-tier attacking piece.
In the opening and middlegame, it is vital to actively seize every opportunity to promote your pieces. A single promoted piece can instantly transform the momentum of your attack.
By the same token, preventing your opponent from promoting is equally important. Allowing a major piece to promote deep in your camp can alone swing the position dramatically. When responding to trades or attacks, always ask yourself: "am I letting my opponent promote something?"