Where to focus?

just want to discuss about acting skills. We already know that we tell a story as we sing.
but how and where we can direct our eyes when we sing on the stage? Do you look at all people /audiences around you?

It is dependent upon the individual. It is best to connect to the audience. I remember being at a David Lee Roth concert when I was a kid. He came flying across the crow on a surfboard aqnd looked down and pointed. I pointed my finger at myself and mumbled the words "Are you talking to me?" although there was no way he could hear me. He shook his head yes and I KNEW right then and there I was special. Funny thing is, I guasrantee you that everyone around me did the same thing, haha. But it was that connection he made to his crowd with the eyes that brought me in.

What to do with our hands? Do we just stand still without doing / planning any movements?

Again that is an individual thing to do. You have to develop your own stage persona;)

How to make our appearance on stages interesting?

Discover your own persona, flow with the music, dress accordingly to the style. Be energetic, connect with the audience:)

yeah there might be a few moments in a rock show that are predetermined, particularly if you are in some huge rock band with pyrotechnics so you don't fry yourself like James Hetfield did.

I think its cool to use your hands to express some of what is going on in the song.  Standing in one spot is fine for some types of music, but then use your hands a bit.  Its important though that you don't overdo it.  I mean you don't wanna look like you are doing the chicken dance, just every other line or so, some subtle action like a clenched fist, or hand over heart or something appropriate you know.  You just have to get in the feel of it.  For high octane rock and metal, its totally cool to be all over the stage.  Although, I did see Judas Priest in Victoria BC Canada two nights ago, and Rob Halford, for some songs, just kinda bends over, closes his eyes and screams his vocals.  Thats more intense then trying to act sometimes.  Its all for you to decide really.  Just be true to yourself.  If you tend to use a lot of energetic body language in every day conversation then it would probably feel more natural to be running around the stage with lots of energy while performing.  If you are more serious when you converse, maybe you would be better with the Halford approach.