I look at 3 things when choosing a plugin

1) Rating

Higher stars tend to mean it is a good coded plugin

2) If it's compatible with my WordPress version

If it hasn't been updated in a while then the chances of not working with my WP ver. are greater chances

3) The amount it has been downloaded

The more people download the plugin, the greater chances it is a good plugin, people won't download crappy plugins, right?

I am sure if enough people complain about a crappy plugin, the plugin gets removed, right?