Taxi Tips:
1. ARESEP is the governing body which licenses taxis/taxistas, sets fares, regulates meters etc. All licensed cabs (yello triangle sticker with license number, red cars) must follow ARESEP regulations or risk losing their licenses.
2. The correct slang phrase is "Ponga la maria, por favor." If you want to avoid offending strict Catholic drivers, use the phrase, "Ponga el taximeter, por favor."
3. With unmetered cabs (not always pirates; 1 in 5 taxistas will tell you the meter isn't working), I offer the customary fare. I say something like, "Tengo solamente ochocientos colones. Podria llevarme al (destination)?" Often, the driver will agree. You need to know customary fares to do this.
4. Be friendly and polite. There's no reason to start out the negotiations with a bad attitude. These guys work very hard for fairly little money. Let them know that you're not new, that you've taken a particular route many times and know the correct fare.
5. Carry coins. I keep a pocketful of 500 and 100 colones coins, just for taxis.
6. As Bilko stated above, tipping is neither required nor expected. One exception to this is if the driver has to help you with baggage or carrying store-bought items into your hotel/apartment.
7. "Tour guides" get an average of $10.00/hour, regardless of distance driven. I have an extremely reliable driver who calls himself a tour guide. It took some arduous negotiation to get him to use his meter for shorter trips, but we finally came to an agreement.
BTW, PM me for his contact information. "Guillermo "Memo" Pacheco is a great driver/guide, particularly for day trips. He's very friendly, speaks some ENglish and knows the valley very well. He also has a regular partner who drives nights.
8. Do not under any circumstances get into a physical confrontation with a taxista. Call the police.