Bubble Free Kapton Tape
Here's a method for laminating your plate glass without bubbles. The secret is to soak your Kapton tape strip in (slightly) soapy water, then lay it on the glass, and gently use a credit card (or the likes) like a squeegee. Having no bubbles is an important step in 3d printer calibration. An uneven print surface yields bad prints and creates unnecessary waste.
Here is a YouTube video on how to lay Kapton Tape with no bubbles.
Insulating the Hotbed Assembly
Insulate the gap in between the hotbed plate and the print surface platform with corrugated cardboard. I found this somewhere online and it totally makes sense.
Lay "chipboard" (cereal box) as a shim(s) on your print platform, then the cardboard on top if the cardboard isn't snug when reassembled.
The reason for the chipboard on the bottom is we want a little give from the corrugated cardboard for the thermistor that's tapped on the bottom of the hotbed. The chipboard is too dense to gently bend around the thermistor.
And any slight bend on your print surface which will create bad 3d prints which is no no bad 3d printer calibration.
After the assembly is snug, take some 2" Kapton Tape and wrap around the edges to reduce any airflow through the corrugated open spaces.
Z-Home: For better First Layers
Never manually rotate your stepper motors when it's plugged in; you will most likely burn up your stepper controller or mess up your stepper itself. Unplug everything before manually moving anything touching a stepper motor.
Only calibrate when your hotbed and extruder are at operation temperature. So, turn it on, heat it up.. Unplug it all and then calibrate.
Your Z home endstop should "stop" the travel on the Z Axis when your extruder nozzle is only 0.2mm from the print surface. This is 2 pieces of printer paper... And, this has to be true on the entire XY plane.
Adjust Left/Right Z Axis threaded rods manually, rotating clockwise and counter clockwise to move each size up or down to get the print head as parallel to the print surface as possible.
Measure the diameter of your filament
It is important to measure your filament diameter and put this into your settings in Slic3r. The higher accuracy the better. Spot check a few other spots down the filament to ensure that the size is consistent. You will run into trouble if your filament goes from (example) 3.1mm to 2.4mm and back... This will totally mess up your prints.
3D Print Troubleshooting Pictorial Guide
Here's a great webpage showing examples of ABS and PLA 3d printing issues and how to resolve them.