Iquitos is widely considered the largest continental city unreachable by road. That leaves planes and boats as the primary means of entrance and egress for both people and supplies.
Do not expect to see a city with all the trappings of the western world. This city is very basic as it has no road connection with the rest of the world. Vehicles are old and most vehicles on the meager roads are "motor taxis" or three wheeler motorbikes which can carry three at a pinch. The people are friendly once you get past the taxi drivers at the airport
By plane
There are numerous flights to Iquitos from the capital Lima. LAN (http://www.lan.com) flies 4 to 5 times per day; Peruvian Airlines (http://www.peruvianairlines.pe) flies twice daily and offers flights without penalties and other facilities. Star Peru (http://www.starperu.com) may offer slightly lower prices but do a brief 10-minute stopover at Tarapoto or Pucallpa on the way to re-fuel and drop off/pick up passengers. Flights are from $55 USD to $200 USD, depending the season and promotions. Is suggested to check prices in all the airlines in advance to get cheap tickets.
When arriving at the airport, consider stopping at the official iPeru, Tourist Information and Assistance Office of the Peruvian Tourist Board PromPerú before exiting the terminal. You can get a free map and brochure without ads!, a list of tour providers, recommendations about what to see and do and safety recommendations. They may help you in case of problems and complaints in all over Peru.
By ship
Iquitos can be reached by boat from any navigable port on the Amazon River. Boat prices will depend on the distance, speed of the boat, number of passengers, and your bargaining skills.