These calibration instructions are copied verbatim from Tim Rastall on G+. They're specifically about KISSlicer but they should work for other slicers as well. I have not tried this yet. He also mentions that Thingiverse object 8757 is a good calibration object.
I've been playing with a few different slicer programs lately. Each has pros and cons. I will try to get some info posted about them at some point.
Firstly, make sure you’ve set KISS to show advanced settings.
Have you done any simple calibration objects? I found the flow tweeks that I had for Kiss were different from Slic3r. So, at the risk of telling you how to suck eggs:
Set your extrusion width for perimeters and infill to your nozzle diameter. Make sure you’ve got it doing perimeters first then insides (better accuracy).
Slice a 20mm calibration cube with 100% infill.
Send it to your printer and let it do 25% of the total layers for the completed object.
Pause the print and examine the infill. If the edges of the infill paths are touching, dial down you flow rate on your printer by 20% and re-commence the print job. Let it do a couple more layers then pause again, there should now be a noticeable gap between infill paths, push the flowrate up by 3-5%, rinse repeat until the paths just touch then add a couple of extra % to allow for variations in filament diameter.
Once you’ve done that and confirmed the cube is dimensionally correct. You ‘should’ be laughing.
If you are still having problems gettin parts to fit, there is an inset surface feature that allow you to pull the perimeters inwards a bit (no more than half extrusion width).