My general rule is-1. Be sure that there is a good percentage of slow airs in each set.
2. The same is true for ballads
3. If people are dancing then play music dance tempo- fast - but take into consideration the skill of the dancers.
4. If no one is dancing then slower tempo should be the rule. Nothing worse than suffering through a band playing up tempo dance music when there is obviously no one interested in dancing in the place.
Take the opportunity provided to draw out the melodies and tunes.
No matter where you are playing people will be there for different reasons. Meditation is one of them. Few bands recognize this and neglect slow airs. Generally people will quiet down for them if they are properly announced. Additionally it is easy to fall into a rut in regard to ballads. Try to get away from the 10 chestnuts and find others. I am also tired of hearing only one side of the political ballad collection. IMHO the most enjoyable set of historical/political ballads contains an even number from each perspective. Here is the unionist side if you dont know the tunes of that tradition. Some are quite ancient and good ballads.
Conrad Bladey