A very simple tutorial,
1) First turn off your device.
2) Press Volume Up+ Home + Power button at the same time.
3) Wait for the SAMSUNG logo to come out. Then wait for the Galaxy W GT-I8150 to show up next.
4) Now you can release the POWER button.
5) Recovery mode will shows up
I always confuse when it come to DOWNLOAD MODE or RECOVERY MODE for Samsung Galaxy device. At the end i figure out the best way to remember is DOWNLOAD mode should be pressing the Vol Down button and vice versa.