M - MUST have this.
S - SHOULD have this if at all possible.
C - COULD have this if it does not effect anything else.
W - WON'T have this time but would like in the future.
Each requirement will have the priority which would be tagged to MSCW. “M” being the highest and “W” being the lowest.
This site gives a very good explanation about this technique.
Business Value Based
The requirement with highest business value is implemented during earlier releases .
Technology Risk Based
The requirement with highest technology risk is implemented during the earlier iterations.
You can read more details about this model here
In this method, features are chosen based on the highest market risk i.e. some thing that is not experimented yet. Release it to the market, get the feedback and apply the learning onto the new feature.
This deck gives a good view about validated learning in the context of lean startup