Exchanging currencies

You don't say where you are from so I cannot totally help.  If you are bringing USD you will be in good shape until you get way off the beaten track.  You can also withdraw colones or USD from most ATM's but you need to watch what your bank in your home country charges for fees.  DO NOT exchange anything at the airport as that will be the highest rate you will pay.  Credit cards are widely accepted (with passport) but cash (USD or colones) will probably get you 10% off at most accommodations.
Questions .... bring them on!

bring small bills like $5 and $10 bills for your taxi ride.  FYI, some cabs have a flat fee to and from the airport.   Last time I used one it was $30.   The current exchange rate ( july 2015) is still around 530 colones to the dollar.  So if my math is correct $30 dollars would be around $15,000 colones.  Also, if you have not been here already, always take your passport to the bank to exchange dollars for colones.  otherwise they may not help you.