The new g-code calibration script generator available at the old address: http://elco.crsndoo.com/reprap/calibrate.html

V2.0 also allow you to chose to print triangle base instead of square base so you can check the 45degree head speed (my printer for e.g. has the firmware bug where 45degree diagonal movement is sqrt(2) faster then only X or only Y movement. You can select feed and flow rate for raft base, raft interface, object, you can select layer height ..

note that extruder speed will be in g-code written as value you enter * 10

1. Enter values into script
2. copy/paste generated g-code into txt file
3. print the file
4. measure wall thickness
5. the wall thickness should be "layer thickness" * "perimeter width over thickness (ratio)", if the wall is thinner then target value decrease feed and/or increase flow rate. if the wall is thicker then target value increase feed rate and/or decrease flow rate (feed rate == head speed; flow rate == extruder speed)

repeat until you are satisfied with the result.