Select the music to suit your audience - don't use inappropriate music. Be aware that some tunes sound dated. They may have been popular when you called them in the 60 s or 70 s, but times and styles may change. Don t be your own worst enemy by calling certain records just because they are in your collection and you want to give them an airing. Use only good quality music unfortunately, some record companies have very thin sounding music.
Scratched records sound terrible .
Look after your records, and replace them or throw them away if they get damaged. Young people have good hearing and will hear the scratches even if the older dancers can't. Minor changes of tempo are OK, but if the entire sound and feel of the original song has been changed, it may loose it's appeal. Most dancers get a lift from these. Try to judge the mood, and use music to suit the atmosphere.