Tips regicide

Don't rush the kills, you can play the game pretty slowly.

If a diamond unit can come next, try to think of what you can do against it, you maybe need to kill with diamond the previous unit.

Try to play spades when a new enemy come.

Against clubs enemy, a good strategy is to play spades to reduce his attack at 0. Then you can play heart, diamond, and low cards a lot. It can be done against heart too, but is less powerful.

Don't be afraid to discard more than what is needed if it's to discard a bad card like a 2. Especially if you hold some diamonds.

Usually when an enemy come you can either try to kill him fast, usually with clubs, or to stall by playing spades. You have the option to try to recover too by playing diamonds (and heart), and let the next player decide what to do with the unit (but then stalling is less effective).

Keeping a low attack (<3) on an enemy is often better than having a 0 attack, except against heart/when you need heart.

When attack of the opponent is low, don't hesitate to yield, it let you discard your bad cards.

Against a clubs enemy, don't hesitate to play clubs if you plan to stall against the future enemies.

Advanced:

(to do: write things about the draw pile which can be managed)