Once your board is layed out, give it the last finishing checks before you submit it to Fritzing Fab:
1. Make a Design Rules Check
Run Trace > Design Rules Check from the PCB view menu. It will alert you to problematic areas that could break your circuit, for example traces that are too close together, overlaps, too little space to the side of the board, etc.
Note that the DRC is currently very sensitive - in dense situations you can also trust your eye.
2. Make a paper placement test (optional)
Use a PDF printout of the PCB view to make a paper placement test. Check if everything is in a sensible position and if the dimensions of the footprints and your actual components match each other. You will be surprised how helpful this step is.
3. Fill up blank areas with copper (optional)
Use Routing > Copper Fill > Ground Fill from the menu to fill the blank areas of your PCB with copper and connect them to your ground signal. It makes your circuit resilient to electromagnetic interference and there will be less chemical waste produced during manufacturing.
Be careful with this step, though: If you have a "messy" sketch where there are some unrouted connections containing connections between ground and power, or if you're unsure, use a plain Copper Fill instead. This will not attempt to connect itself to ground.
4. Save your sketch
Go to File > Save or File > Save as... to save an .fzz file of your sketch.
(In Fritzing versions before 0.7 you need to use File > Save as Shareable)
5. Proof your design (optional)
If you are the super-careful type, you can also proof you files by using a Gerber viewer. Also, we highly recommend this for anyone who is using self-made or community-contributed parts, as these might have some non-obvious flaws.
Learn more about proofing in the FAQ.
6. Upload and order!
Go to the Fritzing Fab order page and submit your file.
When you're done, continue with the Post Fab instructions.