Wool looks after itself better than almost any fabric. It resists stains and odours, so most knitwear needs washing far less often than you think.
Air a jumper between wears by laying it flat near an open window. When it does need a wash, use cool water and a wool detergent, press the water out in a towel rather than wringing, and dry it flat away from direct heat.
Store knitwear folded, never on a hanger, which stretches the shoulders. A drawer with a cedar block keeps moths away through summer.