Best way to get to Koh Phi Phi island from Phuket, Thailand
Koh Phi Phi island is located 45km off the east coast of Phuket, and since there is no airport on Koh Phi Phi, the only way to get there is by boat
Most of the boats depart from the Rassada Pier in Phuket, located here
It's also called Rassada Port or Rassada Harbour. They all mean the same thing
The pier is about 10 minutes car ride away from the town centre of Phuket, 1 hour away from the Phuket airport, and 40 minutes away from the Patong Beach
Getting to the pier from the rest of Phuket is best done with a joint boat/van pickup ticket, which I'll talk more about below in the "How to buy a boat ticket" section. If you don't buy a joint ticket, you will have to take a taxi to the pier and then separately buy a boat ticket. Taxis cost about 500 baht ($17USD) from Patong Beach or the airport and 250 baht ($8.5USD) from town
Arrival pier: Ton Sai Pier on Koh Phi Phi, located here. It's within walking distance the town centre and most of the hotels on the island. It's also spelt as Tonsai Pier, or sometimes called Tonsai Bay, or simply Tonsai, on some websites and guides
There are two types of boats you can take from Rassada Pier: Ferries or speed boats.
Ferries take 2 hours to travel from Rassada Pier to Koh Phi Phi, and cost 350-750 baht ($12-$25USD) per passenger each way
Speed boats take just 1 hour to travel from Rassada Pier to KPP, and cost 1,100 baht ($37USD) per passenger each way
Boat schedule: there are lots of departures everyday, with the first departure at 8:30am and the last departure at 2:00pm, with a boat leaving roughly every 30-60 minutes. The schedule changes from time to time, but you can go to Rassada Pier's website (http://www.rassadapier.com), or any of the booking websites I've listed below to get the current schedule of the boats
How to buy a boat ticket: there are lots of boat operators on this route, and it's pretty easy to get a ticket. My only suggestion here is to book a joint ticket that includes pickup from your hotel in Phuket. Joint tickets are very popular with visitors, because it's much more convenient and cheaper than getting your own taxi to the pier (100 baht for minivan pickup instead of 500 baht for taxi ride). You can buy tickets in one of several ways:
Book online (best option): you can book tickets ahead of time online using local websites; the most well-known ones for Phuket are 12Go, Phuket Ferry, Phi Phi Ferry, Direct Ferries. You can also go to the websites of the ferry companies directly, including Seatran (ferry), Phi Phi Cruiser (ferry), Andaman (ferry), Songserm (ferry), Chaokoh (ferry), Bhundhaya (speedboat), and Satun Pakbara (speedboat). On these websites, search for either Phuket to Koh Phi Phi, or Phuket International Airport to Koh Phi Phi (Ton Sai Pier). They should all have a checkbox option to include pickup/transfer from hotel, which I highly recommend using
Book at a travel agency in town (cheaper option): there are lots of travel agencies in Patong Beach (like this) and the town centre of Phuket (like this). You can just walk into them and ask them to book you a ticket to Koh Phi Phi. Again, ask them to include a pickup service from your hotel in Phuket. At the airport there is also a desk for you buy ferry tickets to Phi Phi. Booking with these agents instead of online is cheaper by about 20%-30%, so this can be a great way to save some money
Buy at Rassada pier (don't recommend): the worst way to book your boat ticket is to get it at the Rassada Pier itself. While this is definitely possible to do, prices are usually 30-40% higher here than if you book in town, and 10-20% higher than if you book online. Also, obviously if you book at the pier you will have to get your own taxi to it, rather than being able to book a joint ticket that comes with a cheap pickup service, so you'll end up paying more for the transportation to the pier as well compared to if you book a joint ticket at a local agency or online.