Where possible always try and create a package option for your products.
This makes it super easy for your customers to make a single purchase rather than having to purchase multiple items.
Say you run an adventure activity business offering white water rafting. Combine your activity with camping, a tour of your destination and even a meal at a restaurant with the guides and the others in the group.
By creating a single rather than multi click option, you may just find a large increase in revenue without the expense of creating new products.