Actively seek out new ways to please each other's mind and body. Learning how to do full body massage is one of the best ways to interest someone in sex with you. Enhance the mood for sensuality by using scented candles and music to relax each other. Try different locations and times to play together. Ask them to show you what really pleases their body.
Variety is what keeps sex from becoming boring.
Don't get into the rut of doing sex only one way. Experiment with positions, touches, toys, etc.