I have been working with a Printrbot Simple Metal. After completing the assembly, I had quite a few problems to start. My biggest problem was getting filament to extrude before we were halfway through the second layer. After tweaking and retesting I eventually ventured to the internet for help. This is when I came a cross an awesome Reddit post which describes a few lines of g-code. These few lines do the normal bed leveling as well as extrude a flat line of filament. This will prime and clean your nozzle so you are immediately ready to start printing. This also helps with strings or other blobs of filament left over from a previous print. Add the following to the start gcode section in Cura.

G90                         ; Explicitly force absolute positioning in case it was not reset previously.
G28                         ; Home all axes.
G29                         ; Auto-level the bed.
G0 X0 Y0 Z0.15 F9000        ; Move to the front-left part of the bed.
M109 S{print_temperature}   ; Set and wait for extruder temperature.
G92 E0                      ; Zero the extruder.
G1 X40 E25 F500             ; Extrude a fat line of filament to prime and clean the nozzle.
G92 E0                      ; Zero the extruder.
G1 E-1 F500                 ; Retract 1 mm.
G1 X80 F9000                ; Sweep right to cut any strings.
G1 Z0.3                     ; Raise the tip a little and begin printing.

On the subject of blobs left over from previous prints. The author of the above gcode also mentions adding the below to his end gcode in Cura. Supposed to help limit the amount of blob left over. I have yet to test this but in theory sounds like a good idea.

G28 X0 Y0 Z0