1. One of the most important things to check, IMHO, is the colour of the warp (or is it the weft?) of the weave - the underlying colour that isn't indigo. IMHO, a sort of ivory/ecru coloured contrast to the denim looks better than plain white (and is more traditional I think).
Tsubi managed to do this well, and to design jeans that you could easily make holes in. However, their denim quality is frankly shite. There's much better for the money.
As for what to wear them WITH, it all depends on the colour. But, the usual, tshirts, boots, Chucks, leather jackets.
I think the ripped idea goes with a more fitted silouhette, straightish legs, etc. You don't want to be rocking a baggy tshirt and 4 inches of selvege.
2. There are, though I also recommend damaging your own. If only because there's a premium price for the labour, and if the holes (say, at the knees) don't conform to your anatomy, it looks hell stupid. Also, you want them to be personal, not off-the-shelf custom.
3. I recommend unpicking a few threads at key points - knees, front pocket edges, back pocket where the wallet goes - and letting nature take its course from there.
4. If you really think you can make it work. But, I think there's a real risk of looking affected. I've done painting in my jeans, and a few stray marks look cool, but there's a risk of going overboard.
That said, I have one awesome pair (that were a one-off done by a local artist who also happened to work retail) which are very dark blue, slightly shiny denim. There's black paint sorta creeping its way up from the bottom of the legs in splashes...it looks very cool, either like I've stepped in an oilspill, or like evil is slowly taking over my jeans.
They don't fit me too well, so there's a chance I may flip them...