A general rule of cleaning DSLR sensor by yourself is, not to do it! If you insist however, here are the steps to follow to increase your chance of success.

1. Have the sensor swab ready. They often come with different sizes that fit different camera sensors.
2. Clean the lens (front and back) and mirror first using Air Blower and LensPEN.
3. Set the lens to Manual Focus (MF) mode, set Aperture to 16 and ISO to 100. Take a picture of a sheet of white paper. Double check if sensor cleaning is required.
4. Remove the lens from the camera. Use the configuration menu to set the camera to Sensor Cleaning mode – now the mirror should lift up.
5. A couple of sharp blasts from the air blower to dislodge the dust.
6. Apply no more than 3 drops of cleaning fluid to the swap. This is very important – the residual of water is much worse than the dust.
7. Don’t blow air to the sensor after cleaning. It only gets dust onto the sensor instead of removing them.
8. Place the swab on one end of the sensor, put enough pressure to bend the swab, move one direction across the sensor and return for another across.
9. Turn off the camera to close the mirror, put on the lens and shot another picture to see the result

I was frightened by what I saw after using the first swab. It’s much better after 7 or 8 tries. Finally after the 11th swab was used, I got a clean sensor.