Some 3D printing problems and what worked for us.

3D printing takes time and effort. The print might not be the best one in the first try but that's okay :) . It took us weeks to get a decent print of a cube.
Problems­  ­Solutions
Not extruding during the start  - Increase the skirt width - Check if the nozzle of the extruder is clogged with the filament.
Print not sticking to the bed -Increase the bed temperature -Level the bed or change the Z offset -Use tapes for better adhesion -Increase the extruder temperature -Maintain appropriate speed. Initially perform the print in lower speed and gradually increase the speed until you reach the optimum.
Stringing -Decrease the temperature -Increase the retraction speed and distance.
Warping ­ - Use a heated bed.
Dimensions of object not accurate­ -Calibrate the default axis steps per mm in the firmware itself which is an iterative process. -Level the bed
Poor Bridging ­ -Increase bridging speed and increase cooling of the print(fan speed).
Poor strength of the print­ -Increase the number of solid layer -Select appropriate infill pattern and density -Print at higher flow rates
Over extrusion­ -Decrease the flow rate -Decrease the temperature of the extruder
Under Extrusion­ -Increase the flow rate -Increase the temperature of the extruder
Unexpected stop of the print­ -Check if the motors are overheated, and if so, decrease the current.
Gaps between the printed lines -Increase the perimeter overlap. -Increase the flow rate.
Inconsistent Extrusion -Check for the clogged extruder nozzle and the extruder gear. -Incorrect extrusion width.