At the airport in Lima, simply go to the taxi stand on the lower level. It's behind the escalators and next to the left baggage office.

They speak some english, are very professional and will quote you a set price before you pay them in advance of your trip. The drivers all wear ties and a white dress shirt, are polite and will use air conditioning if you ask. Airport to Miraflores will run you about $15 USD.

For your return, I would advise against hailing a taxi on the street. Simply walk into any hotel and ask them to call a taxi for you. If you go to the Larcomar shopping area (outdoor mall on the ocean) in Miraflores, you will find a taxi stand on the lower level near the restaurants.