Before anything else, identify the exact car: model year, engine code and gearbox type. On VAG cars these three facts determine the oil specification, the timing drive type (belt or chain), the service schedule and most of the known trouble spots. The vehicle data sticker and a basic diagnostic scan will give you all three in minutes.
After that, verify the service history against the items owners most often miss: DSG fluid changes on wet-clutch gearboxes, Haldex coupling oil on all-wheel-drive models, timing-belt status on belt-driven engines, and evidence of quality oil meeting the correct VW approval. A car with gaps in these areas is not necessarily a bad car, but the gaps should be priced into any purchase decision and closed promptly.