Once the bed is successfully calibrated you can begin printing. Load the filament into the printer via the printer's instructions. For closed source printers, there usually are very specific instructions you follow on screen. For the Makerbot 5th Gen, you just guide the filament in until it clamps down on it and begins extruding it. For RepRap designs, you may have to hold down a spring lever in order to allow enough space for the filament to go though. Once filament begins extruding, you can let go of the spring and it should clamp down properly. If the filament extrudes in neat piles (preferably circles) and without making popping sounds or releasing steam (humid materials issue) then you are ready.
Accessories that can affect printing:
Heated Bed - a heated bed will allow prints to stick a bit better than printers without. Heated beds can easily go beyond 50 degrees Celcius/122 degrees Fahrenheit. This means they will burn you if you are not careful.
Heated Chamber - a chamber that is warm means better layer to layer adhesion for layers beyond the first. They can propagate more fumes and smells however, so a face mask or good precaution is necessary.
Spring Loaded Extruder - if there is a level on the extruder, this generally implies that there is a spring within the assembly. This is to provide more reliable use for filaments of varying qualities (if a filament is not consistently dimensionally accurate, it can have deviations of 1.75mm or 3mm +/- .5mm) and will allow more exotic and inconsistent materials (such as wood fiber or carbon fiber) to be printed out
Z-Probe - a probe can come in many forms, but it essentially pushes the extruder assembly down until a limiter switch is triggered. This can provide automatic leveling on the gcode side (it will alter gcode values) but if the probe is not securely attached or the bed is serverely uneven, it still will not print 100% correctly