|Licensed taxis at ferry port,|
To start with, there is nothing wrong in having a friend drop you off or pick you up at the airport, even if you pay for the petrol. And who's to know who's charging for what, anyway? (Answer: your conscience)
Things start to go wrong when there is no friend available and a proper, licensed taxi is needed.
Arrival arrangements can contain pitfalls
On arrival, the matter is simple: you head for the taxi rank and take, yes, a taxi. A piece of advice, though: if going far (more than 15 minutes, say), settle the amount beforehand - in some cases, you will notice that the driver may stop his clock or not set it, or whatever. This probably means he has agreed with you to get more than the clock would allow - no matter, if you're satisfied with what you agreed to, so be it. If there's any way you can find out what the customary fare is, do so beforehand.
If you're headed for another town or village, as is so often the case on the coast, it is best to use a taxi from the rank at your arrival place, rather than make arrangements to be picked up by a taxi from wherever you're headed. The reason for this is that local taxis do not want 'intruders' from anywhere else, no matter how licensed they are. In some places - we have witnessed it at the La Línea frontier rank, and at Málaga airport - the local drivers can get very aggressive indeed and not only with the driver but also with the passenger.
Leaving arrangements are easier - maybe
If you're on holiday and need a taxi, you're a target. Sad but true - anywhere in the world it's true.
So the best thing is to try to find out what the cost usually is for the fare between where you are and where you want to be. Ask at hotels, bars, whatever, but ask. That way you have an idea and can pooh-pooh outrageous deals - there's no need for language, a shrug of the shoulders and walking away says it all.
Most small town taxi drivers are more than happy to make arrangements well before the time they are needed. A few days before you're due to leave, go to the nearest taxi rank and tell them what you need. They usually have enough English (rarely anything else, but possible) to understand that you want to be picked up at the holiday home you're in. Can you rely on them? They need the business these days, so probably, yes.
Bare in mind that ideally, your local taxi would dearly love to pick someone up for the return journey, but he won't be allowed to do that when you're dropped off at the airport. This might be used as a 'price riser' but it's not your problem. There is usually a fairly standard rate in any case.
Also, any holiday rental property worth its salt should have a list of useful phone numbers, among which should be the taxi rank's as well as a couple of mobile numbers for individual drivers, with most of whom you can make private arrangements if needed.