I talk a lot about how working memory constrains what we can process and remember, but there’s another side to this — long-term memory acts on working memory. That is, indeed, the best way of ‘improving’ your working memory — by organizing and strengthening your long-term memory codes in such a way that large networks of relevant material are readily accessible.
Oddly enough, one of the best ways of watching the effect of long-term memory on working memory is through perception.