How do I choose the right wheel offset for my JDM car?

Start from your car's factory offset and the wheel width you want, then work outward. Wider wheels need lower (or negative) offset to clear the suspension while filling the arch; go too low and the tire pokes or rubs the fender. The safe method is to copy a proven fitment for your exact chassis and wheel size, then fine-tune poke with hub-centric spacers rather than guessing on offset alone.