This is how you knit a domino diamond. Make several for your starting row. Then pick up sts along sides of two diamonds and work another diamond. Always make sure to slip 1st st on each row, and knit the last one, then you will have a nice edge on the diamond to pick up sts in afterwards.
WS rows: knit if you are working in garter, purl if stockinette.
RS rows: knit all sts and work middle 3 sts together to 1 stitch by: slip 1, K2 tog, pass slipped st over.
Pull yarn through last st on diamond.