My 2001 Honda Odyessy wont start. All I get is a clicking sound coming from underneath the hood and the light do not work.
The clicking sound on cranking is usually a strong indication of a weak battery that needs replacement. This is also corroborated by the fact that the lights don't work.
If the vehicle can be jump-started it will confirm that the battery isn't charged. Have the battery tested if this is the case and replaced if need be.
If the battery is good, and the lights do not work, it may be the "fuseable link". A short lead close to the positive terminal. If this is blown it requires looking into. If it is loose or not plugged in you should be OK. The Starter relay does not depend on this, but the car will not run without it. I would expect it to crank though, so maybe you have a short somewhere or the starter is on the way out. Try having someone tap the starter with a broom handle to "encourage it".