The only things you can do in advance is to dice the Pancetta and mince the garlic.  This should only take a few minutes, so you can do it 3-4 days in advance or right before cooking.

Bring a large pot of water to a boil and then add a tablespoon of olive oil and a teaspoon of salt.  Add the spaghetti and stir while cooking for a minute so the pasta doesn't stick.  Bring back to a boil and cook for 7-10 minutes until it reaches desired consistency.

While the pasta is cooking...Preheat a large skillet on high.  Add the diced Pancetta.  You shouldn't need any oil in the pan as the pancetta has a lot of fat that will render.  Stir the meat around with a spatula to prevent it from sticking.  Cook about 4-5 minutes until the fat is rendered and the Pancetta pieces are just starting to crisp.

Turn the heat down to low and add the minced garlic and juice from half a lemon.  Stir and cook for 2 minutes.  Then turn off the heat.

Scoop the pasta out of the water and add it to the skillet, saving the pasta cooking water.  It's ok of you get some water in the skillet with the pasta.  Drizzle the pasta with a tablespoon Extra Virgin Olive Oil and then mix the pasta with the pancetta, garlic, and lemon juice. 

Measure out a cup of the pasta water and let the pasta and the water cool to warm, not steaming hot, about 10 minutes.  You do NOT want the cheese to melt into clumps when you add it!  After 10 minutes, add the parmesan cheese and ground pepper to the pasta and immediately combine the parm and pasta using tongs or a couple large forks.  You want the parmesan cheese to coat all of the pasta.

Last, drizzle in the water a little at a time, each time mixing until the parmesan starts to get creamy.  If it starts to clump, the water is still too hot and you need wait until it cools a bit more.  Continue this until you have added all of the measured out pasta water.  You can always add a bit more if needed.  That's it!  Serve and Enjoy!