yeah. what he said.
As far as extrusion rates and the like - I've never messed with them. And never needed to.
Shells can make hollow or sparese infilled objects stronger. I pretty much use 2 all round for most things. For hollow models I might go to three. And if I want something strong and I'm using s3d I might even go to 4.
Also when you adjust printing temps - do so in small increments.
Jumping from 180 (think it was around there) to 220 is kind of one extreme to the other.
Go up in 5c increments with a small complex print and stick with the print that looks best.
This is my test object:
Attachment 4194
Basically a cube with a sphere removed. If you can print a fairly clean version of this - then you're good to go on pretty much anything else.
Plus it only uses about 1 gm of plastic :-)
Attachment 4195
The middle section is particularly difficult, great test for extrusion temps.
If you can knock one out at 0.3mm then you've got a really well calibrated and setup machine. I usually print it at 0.2mm.
It also tests everything else from under hangs, over hangs, bridging, precision of placement, retraction (amount of stringing) and anything else you care to think of.
IT's useful to have a benchmark file that you know what it should look like. That way when you try new settings or filament you can knock one out and adjust till it looks right.
Bear in mid that 3d printing - as we currently do it at home - is still as much an art as it is a science.
And we're all operating our machines at different temps, humidity levels and altitudes (air pressure effects expansion rate of hot materials). So what works for me - might not necessarily work for you and vice versa.
The only things I regularly mess with are extrusiuon temps, layer height, shells and print speeds. And i can pretty much print what I like how I want it.
You can change too many things and then not know which change made the crucial difference.
And from experience. The two most crucial things are extrusion temp and a really really level bed.