Well, sometimes, when reading a schematic/diagram, it'll say what type of cap is most preferable and useful in that specific area. Sometimes you can tell what type of cap to use by the capacitance and voltage, ie; a 1200uf 80v cap, would quite obviously not be a film or ceramic type but an electrolytic. Electrolytics are pretty much always the ones with the higher capacitance, around 10uf and up in most cases. Film and ceramic are used usually for 10uf and under, these types can quite often be interchanged with no damage done. Of course, there are electrolytic caps lower than 10uf and film types over 10uf, but there is a limit (if size is an issue). For example, when working with ps's, usually the caps will be electrolytic or ceramic, audio projects will usually use film types(when asking for lower capacitances) but in this situation is not recommended to exchange film with ceramic. I really havent read up on what cap types are used for what but am "writing" from experiance.
ivan c.