Linen only gets better with washing. Unlike most fabrics, linen softens and improves each time it's laundered, so there's no need to baby it. Machine wash cool on a gentle cycle with a mild detergent — just don't overload the drum, as linen needs room to move.
Make peace with the creases, or beat them. Rumpled linen is the whole point of the fabric in summer, and a relaxed shirt or trouser is meant to look lived-in. If you want it crisp, iron while still damp on a hot steam setting, or hang it straight off the wash to dry and let gravity pull most of the wrinkles out.
Line dry and don't over-dry. Linen dries fast; pull it off the line or out of a short cool tumble while there's still a little moisture in it, which keeps it from going board-stiff and makes any ironing far easier.
Store it breathing. Hang shirts and fold trousers loosely somewhere airy. Linen resists moths better than wool but still dislikes damp, so keep it dry and it'll last for years of summers.