Always check last piece played by the other player and those behind

Approximative value of the pieces :

Pawn = 1

knight and bishop = 3

rook = 5

queen = 9

king = infinite

Opening tips : Try to castle early (the king is usually safer on the side, and out of the way), take the center (occupy it with your pawns or control it at dstance with bishops), develop in priority knights and bishops. Rooks are clumsy early game but become stronger later on.

don't attack with your queen too early unless you see a good reason too (weakness in your opponent's defense)