- Plan first: I knew what I wanted to produce, and thought I had it all worked out, but I didn't. I've torn down my setup on 4 of 5 planets at least twice now. Part of that was poor planning. I am still tweaking the setups, and at the cost of a few million ISK each time it does get annoying. I could have planned even more and maybe had some of those stable from the first setup.
- Watch your processor loads.This one came to me just yesterday, and resulted in some of my rebuilding. Depending on the extraction cycle, you can overload your processor, which (I'm assuming) will lead to lost/wasted resources. Keeping track of the % of incoming materials to the processor and making sure it doesn't go over 100% (by much) will ensure you get maximum return on extraction. On the flip side, the extraction cycle you choose can affect the percentage of incoming resources, it seems, so it may be worth considering storage silos for large extraction sites - with a two way link between the processor and the silo to get the materials processed and safely stored. I'm still working through this, but I'm seeing a logical reason for silos more often than my initial setups anticipated...
- Profitability levels: I don't know if anyone is getting rich on raw PI production. I know (from experience) that the activity/profit level seems pretty high for me, since I am doing 24 or 96 hour cycles, so I don't babysit much. However, my setup is not providing the volume of materials I wanted, so the activity/profit level may be lower for useful production. As a byproduct it's not so bad just hauling stuff to trade hubs every week or two.
- Command Center or Spaceport... So I initially installed Spaceports on all my planets, to take advantage of the customs offices. I'm rethinking this on planets where I don't need Import and the volume is small. The PG freed up from a Spaceport for an additional extractor (or longer links) is tempting on T2 production. Don't automatically assume you need a Spaceport, and make sure your Command Center is close to the processing area - just in case you need to use it for a launchpad
Start with one planet, and one process, whether it's a T1 or T2 product. Start simple. Cluster your extractors close to the first T1 processor to keep the link PG low. If you are trying to get a lot of material, add a silo between the extractors and the processor, with a two way link. If you aren't importing goods to the planet, consider using the command center as your launchpad - and apply the PG/CPU to more extraction or processing. Once you get one planet all setup, move to the next. If you are doing similar processes on similar planets, set up all those first. I did my Gas/Storm setups first to get the easy Coolant and Oxygen processes running, and since they are end products (in my chain) and there is no planetary import, I use the Command Center as my final storage and launchpad.
My robotics chain is more complicated, since I didn't have a convenient planet to run the whole chain in one place, so on my Barren planet I'm using a Spaceport for Import and Export, and (conveniently) it's a silo for the process materials as well. Two-way links FTW.
If you are just getting into PI for profit, you need to do the prerequisite research. Check the various product prices on the markets, and figure out where your top profitability lies, based on the planets available to you. Build the biggest Command Center you can. Seriously - train that skill to L4 if you didn't already. 17k PG goes so quickly you'll start rearranging your extractors and processors to minimize link distances and create shortest path links. I often use EVE Central for price checking - it's a great resource in or out of game so you don't need to log in that Jita alt.