Most people want to use a certain plugins, however they do not know if it's good or not! Here is how you can know!

1. Find a plugin page
2. See if there is any comments down there saying good! or not.
3. See If there is a lot of features, descriptions or not.
4. See if many people download it or not.
5. Check if there is any video tutorial or examples.
6. See if the plugin is useful or not!
7. Check the maker's profile to see if he/she is experienced and have make a few other plugins!
8. Have everything above? Download it!

Extra:
check out other's server and do /plugins to see what plugins are good~!