Whenever my priest husband gets asked this question, there is this little gleam in his eye. I know what he is going to say in response, "I'm not giving anything up!" He'll wait a beat or two to allow the questioner's mouth to gape open a bit, scandalized that such a faithful priest wouldn't give something up for the Great Fast.
Then he will continue to answer the question in full. "During Lent we are trying to unite ourselves to Christ and His passion through fasting, charitable works and increased prayer, so I'm going to _______ during these forty days. How do you feel called to observe this time?" And then, the questioner usually says something about giving up chocolate.
Now, there is nothing wrong with giving up chocolate. Renouncing a favorite food can be a really effective reminder of which season we are in- rather like a rubber band around the wrist that one uses for behavior modification. It's just important to keep the focus on Christ and trying to be more like Him. Besides following my rite's guidelines for the fast and increased prayer, I am trying to DO more this season- like bring out the sewing machine to work with the girls or color with and read more to the little ones. As a 'lazy, low-energy introvert,' it will be a challenge to do these positive things when practical cooking and cleaning is calling my name, but they are important.