Depends what you are searching for.

If you are using LW 5 or WireShare & open the Advanced Tools from the Tools menu bar option, you will be able to see incoming searches. You can get an idea of what are the popular search terms this way.

There are some clues about searching for things discussed around the forum. Such as being too specific in your search terms will bring in less search results. Some files might not be named as you might expect. That's a user population issue. So varying your search terms might help considerably. The network is quite dynamic. Hosts leaving and new ones starting their session. Likewise the ultrapeers you are connected to will change over time. So different times of the day might bring in a variation of search results. Even an hour or two (or less) can make a difference.