Have officer groups with clear goals and structure.
Change voting procedures in order to make them more like the UN, potentially with a roll call to provide further transparency.
Create fundraising goals. Meet them by (among other things) creating merchandise for MUN (that would also provide club advertisement) and provide food at meetings.
Have a meeting dedicated to reviewing/revising the club constitution.
Have more social events (e.g. conference themed parties, movie nights).
Have field trips!!
Have officer updates at meetings. Use this time to bring in more voices, and provide more transparency and accountability in the behind-the-scenes work of the board.
Continue to look back upon these goals and evaluate ourselves, adjusting them as need be.