One of the classic mistakes that people make in planning agile software projects comes about when someone is asked to prioritise the stories to be done by the software team. The conversation usually goes like this:
Q: What do you think about Story A?
A: That's a priority one.
Q: Ok, what do you think about Story B?
A: That's a priority one as well.
At this point, the stories have not been prioritised. They have been classified into groups, where the group is named "Priority One". Whilst this may be a useful culling technique, do not fool yourself into thinking they are prioritised. What's worse for you is that, whether you like it or not, the stories will get done in some order. If the team is ready to start on a story and finds two of them that are both "Priority One", then they will pick one of them to do first. Sometimes, they will pick the wrong one.
Do your team a favour. Don't classify your stories. Prioritise them.