map objectives?

One day i talked with some other et players about what could be done in map design to make the et matches more exciting. You know et is out for several years now and the official map pool mainly consists of modified standard maps and rtcw conversions. Only a few times new maps where taken into the pool but if that happend they really turned out to be an enrichment to the game. So what i like to know is what are the main things a map designer should take care of to build not only a good looking map but also one that can be played in competition. For example should the map be constructed in a way to prevent the ability to spam spawns or should there be limitations in the mapsize? Im looking forward to hear your opinion

greetz Maffe