for Screebshot is:
Press Power Button & - (Volume Down) button.
Keep it for 3 seconds atleast until You get a notification of Screen Shot in any form.
According to a User at GSM ARENA:
"Hello, if u want to take a screen shot then press lock button given right side and on the same time low volume button.....U will get a notification of screen shot ... " Source: *www.gsmarena.com/xolo_q1000_opus-reviews-5906.php
If this is does not work,
Power Button & + (Volume Up button.
Power Button & Volume Button Both
Press Simultaneously for 3-4 seconds
not just for a Flick of Second.
In Samsung it works as :
Power Button & Menu Button simultaneously for 3 seconds.