Ive tried searching on the net but can only find conflicting information. We are looking at heading over to Krabi from Phuket and would like to get some info on if there are any buses available, and if so, where to buy tickets and then hop on the bus.
Also, is there a minibus service running this route too?
I can't help you with specifics, but there will definitely be busses running to Krabi. Phuket must be teeming with travel agents - I would pop into one of the agents, or ask at your hotel/guesthouse and they will be able to sort out a bus for you.
Got to be buses just about hourly from the Phuket town bus station - Phuket buses http://www.phukettourism.org/other/bus_time_phuket.htm
There are also minibuses - any travel counter or hotel/guesthouse should be able to book you.
Now if you want to go from the airport it gets a lot trickier because Phuket airport is 35-40km from Phuket town and the main beaches Which are the opposite direction to Krabi . Airport axis will take you direct as will the limo services for maybe +10-20%, but these aint cheap.
You can get a taxi the 4km or so out to the main road and wait for a Krabi bound bus to pass, but this is not as easy as it may sound if you are new to Thailand.
Buses are regular from the governement bus station until about 7pm.
I have not travelled on a mini bus in Thailand for almost 5 years. They are notoriously uncomfortable and the aircon hardly ever works...miserable.
Tezza is right about the Phuket airport consideration. This can add considerable time to your journey. There is a short piece of information on this particular part of the trip on my website at a) ii). Just replace 'Ranong' with 'Krabi'