Pretty much oil.
Keep your filters clean.
Flush the radior, make sure you have fresh fluids for powersteering,brakes, diff, gearbox, washer. check for leaks. replace brittle pipes
Perhaps a sillicone spray on the plastic bits, make sure all 4 are firing properly, and she will run.
My dads partner just sold his E36 with 630,000km on it, and no thats not a typo...