When to Tighten Spokes?

Generally it is preferable to tighten spokes rather than loosening them – spokes may loosen themselves over time if they are run too loose, but they will not tighten up on their own.

How do I know if my spokes need tightening?

1) Rattle and Hum: Tighten Those Spokes

For the most part, you shouldn't hear a lot of 'rattling' from your ride. If you notice a rattling sound when you pull it down from your hangers, or when you cross a fence, take note. It's a common problem on vintage bicycles. Try to narrow down the source?

Is it bad to have loose spokes?

Never ride with a loose spoke. The friction created will cause the rider to burst into flames and may even cause the Earth to slip off it's axis.