I have been stack for 2 days, but have not received any reward in any coins. Simply turn on the "stacking" and wait for the result?
i m staking since day 1 (when pos activated) and no hits, on the other hand a friend is staking from day 1 as well and has 3 hits already. bad luck brah

Oh, it's depends on Luck? Bad news for me ) But anyway I will continue stack, no problem for me keep wallet open.
To make sure that your wallet is actually staking, you can go to Settings icon > Advanced Options > Console > and type in:
getwalletinfo
If "staking_active" says "true", your wallet is staking. If not, you may have to restart the wallet or toggle the Staking button off and on.