For example; if you want your car to be a lowriding with huge chrome rims, then you'll only need to purchase some large sized rims, around 17-18 inch, four corresponding low-pro tires, and either coil-overs or cut racing springs. So, you need to get in your mind what you want it to look like, so you can search for those parts.
Another aspect of the Planning Stage is deciding where you will be buying your parts from. This can be the most infuriating stage. The reason for the said frustration is most places who ensure safe shipping also have exhorbitant prices. The cheapest way to get parts is on Ebay, but this is unreliable at best. You also don't want to buy from overprices places, such as Veilside or Bomex, who overprice their parts for namesake value. Usually the only difference in these parts from the others who may be generic but still 'look' the same is pre-drilled wholes and emblem indentions in odd places, hardly enough to warrant the heightened prices.
After you've decided what you want your car to look like, and figure out wher you will get these parts, you come to the final step of the Planning Stage -- Evaluating Funds. This step can have the ability of cancelling out other parts of your planning. That is, if you envisioned this car to be this grand spectacle upon completion, and want to buy all your parts at the highest retail value to ensure safe shipping and quality of parts -- but only make 50 dollars every two weeks, you may want to envision a less grand end result, or get a second job.
Evaluating your funds could also be called "Creating a Budget," because that is what you need to do. You already have the parts you want in mind, so you should budget ou when you will buy each product while making sure to allow for spending money and any emergencies that may arise. My budget spanned for over six months of buying and saving before I had ordered and received all of the products for my car, and that was without saving up for the installation.