Your bridesmaids may help shop for bridesmaids' dresses and co-host the bridal shower or bachelorette party. They may also help you put together favors or other DIY projects.
Be clear about which duties you expect your bridesmaids to perform when you asking them to get involved. This helps avoid any issues in your wedding plans, as wel as the awkwardness that could result from a bad experience. To give your potential bridesmaids plenty of time to prepare, try to contact them shortly after you announce your engagement.