The Rat's Proposal is the the first part of Act II in Stronghold's military campaign. The rat offers to parlay, but lays a trap instead.
To start your keep, place the keep somewhere in the south-east corner, where there is a cluster of trees. This allows your woodworkers to quickly provide wood without having to travel.
Build your farms. You will want a mix of food, the easiest being the dairy farms although you should be sure to provide meat and bread.
Once your wood economy is functional, build fletchers. This allows you to get as many archers as possible to defend against enemies.
Build your quarries in the southwest. Only one quarry is needed.
Build the wall and gatehouses to the north - remember that you can't build too close to the sign posts, thus you should leave enough room for the crenellated wall.
The rat will eventually send his forces. If the wall is solid, you will be able to repel them easily. Note that his attackers will use ladders - if possible, build your wall in a way that allows them to be attacked easily.