Do you have a pilots license? Do you know about fronts, convection, saturation, dew points, lapse rates and things like that? Clouds can tell you something about the weather, but you've got to understand how and why the clouds form before you can predict things. At the end of the day, this is because clouds are only the visible parts of weather. There's a lot of things to weather that we cannot see. Eg. temperature, wind, saturation.
But if you just want to impress your friends, here's the basic system:
- Any cloud which looks fairly flat is called "stratus"
- Any cloud which looks fluffy and like a coliflower is called "cumulo" or "cumulus"
-> Cumulostratus is a layer of coliflowers
- Lower level clouds do not get anything added to their name
- Any medium-level cloud gets "alto" added
- Any high-level cloud gets "stratus" or "strato" added.
-> Altocumulus is medium high coliflowers
-> Cirrostratus (sometimes just called cirrus) is a very high, flat layer of cloud which looks like a bridal veil
- Any cloud where rain falls out of is called "nimbus" or "nimbo"
-> Cumulonimbus is a coliflower cloud which produces rain (most often thunderstorms)
-> Nimbostratus is a layer of cloud which produces persistent rain/drizzle
All these different clouds have abbreviations too, based on their name. The ones most important for pilots are TCU (Towering Cumulus - a very tall coliflower which holds a lot of up- and downdraughts so you really don't want to fly through them) and CB (Cumulonimbus - Usually a thunderstorm with all the effects of a TCU, plus heavy rain/hail and lightning.)