How do you reset check engine light on 1994 geo?

It seems that on most cars 1994 and earlier, disconnecting the battery for ten minutes will do it. I saw one site which advised disconnecting the positive cable but it's usual to undo the negative one.

If you are talking about a Metro or Tracker there is a tiny switch in the front driver side speaker you can literally flip and it will turn the light out the original Metro and Tracker were set up that the light came on every 50,000 miles to remind people of a major service was needed.