To reduce bounce rate start with a clear un-clattered design so that users find it easy to navigate.
Don't bombard your visitors with ads and/or irrelevant material, make it clear from the beginning.
If you have a custom 404 page, to ease the frustration when the visitor don't find the content, it will be better and more friendly.
Take a look at your site, is it a site that you'd like to go back to over and over?
Finally, place your social media links, contact info, in a prominent place and make sure to place the share buttons correctly.