How to select a good quality frame? I have asked a lot of questions here, and most of times, the answers that I get is related with having a good quality frame. But, in my nation, store owner (or mechanics) hardly give any detail regarding any frame, they just see the price and judge a frame as good or not so good. 

How exactly to select a good quality frame? 

I ride a typical MTB, for commuting, offroad riding, road or touring as well.

I am expecting in terms of material, weight, welds and other relevant areas (which is obviously dont know of).
I think most any frame is going to suit you just fine -- consider size, riding position, cost, and weight. Outside of that, one generally doesn't have to worry about frame failures or anything of that sort, with the exception of crazy carbon racing frames.

I think this is the point where you go to a local bike shop and try a few of them out -- look at what's available, and choose one you like (that is, that you feel comfortable riding with).

As far as things like welds, you really don't have to worry about the frame failing on you. Better welds are lighter, but that's really the extent of it.