The ESP8266 can be programmed using the Arduino IDE. The best part is the codes are similar to Arduino. To start programming a ESP8266 using Arduino IDE follow the below steps

Prerequisites

• Arduino 1.6.8, get it from Arduino website.

Steps

• Start Arduino and goto File-> Preferences.
• In the “Additional Boards Manager URLs” Enter http://arduino.esp8266.com/stable/package_esp8266com_index.json  (You can add multiple URLs, separating them with commas)
• Click “OK”
• Open Boards Manager from Tools -> Board menu and find esp8266 platform.
• Select the version you need from drop-down box.
• Click install button.
• ——————————————–
• Upload a blank sketch to the Arduino.
• Connect RX to RX and TX to TX
• GPIO_0 will go to GND
• VCC and CH_PD will go to the 3.3v supply line
• Select the appropriate ESP8266 board from Tools > Board menu.
• Select the appropriate Flash mode (DOUT or QIO. See notes below)
• Other parameters works mostly as it is – but still check once.
• Start upload
• RESET the module. This is a critical step and the timing matters. It may need a few tries to get it perfect.

After the code uploaded

• Disconnect GPIO_0
• Reset

For further details please check http://esp8266.github.io/Arduino/versions/2.3.0/

Please see this article for a basic code (Blinking LED that is the Hello World of micro-controllers)

Notes

• While uploading codes through Arduino IDE select DOUT for new chip and either DOUT or QIO for old chips.
• Keeping it to DOUT will work for both New and Old chips.
• Burning new chips with QIO (or inappropriate modes) will result in a successful burning but the code will not run.

Here is a Troubleshooting Guide and parameters that worked for me.

Flashing guide for new chips.