If you're driving to Newquay, you can take the A30 if you're coming from Exeter, Bristol, or London. From Plymouth, you can take the A38 before joining the A30. If you're coming from the north or east, take the M5 until you reach Exeter, and then follow the A30.
If you're taking the train, Newquay has its own railway station, which is well-connected to other stations in Cornwall and beyond. From London, you can take a direct train to Newquay that will take around 5 hours. If you're coming from other parts of Cornwall, the branch lines from Par and Truro are the easiest ways to get to Newquay.
If you're looking to explore other attractions while in Cornwall, you may want to consider visiting the Eden Project, which is around an hour's drive from Newquay. You can also visit the historic town of St Ives, which is about 45 minutes away by car.