By Bus: You can take the Sita bus from Sorrento, Naples, Amalfi, Vietri and Salerno. Make sure you take a window seat to enjoy the outside view. When you are travelling from Sorrento, choose the right side window seat and from Amalfi to Positano, choose left side window.
By Car: If you are taking your car, take the autostrada A3 from Sorrento. Watch out for the signs like Vietri, Maiori, Amalfi and Positano. These signs will lead you the coast line of Positano. At the same time, reserve a parking area beforehand if you are travelling at peak time.
By Air: You can fly till Naples. From there, you can hire private taxis to reach your destination.
By Boat: Ferry from Naples available. Though it turns out to be a bit expensive as compared to the bus, but it saves an hour and also offers a striking view of the mountain cliff along the coastline.
HOW TO GET AROUND POSITANO
By Bus: Local bus company, like Sita bus company runs from the town to the coastline. You can try the bus to take a tour around the city. It is one of the convenient and budget friendly transportation of Positano. Although, the bus doesn't span over the entire town and you might have to get around by some other means.
By Car: Private cars are available, but arrange it beforehand if you are travelling during summer.
No matter whichever mode of transport you take, the roads are bound to be crowded during peak hours. Especially during summer, it's hardly possible to get a seat in a bus. Hence, avoid travelling during those hours.
Apart from them, if you have strong legs, walking down the road will be the best option. It will save you from getting stuck in the jam for long hours. Walking along the cliff and high roads of Positano also gives you an experience of hiking.