hey silence sky
yes, one look can tell that the picture is heavily tilted to the left
there is also lens distortion problem
not sure about keystone, will have to see, but probably has too
i usually just try lens distortion of +6 correction in ps, which i did here
rotate 1 degree clockwise, - now to check whether the picture is correctly verticalled, the easiest way is to just check the building in the centre
if don't have then suck thumb, but here have, the one with the blue logo in top right
after rotation i based using the rectangular marquee tool as straight edge
then now, vertical perspective correction of about -15
after cropping, result:
still not very well adjusted but smaller pictures very hard, i have to base it on eye, cannot zoom in to be exact
so the building on the right still not very straight, hrm
so this was a very botched job but i guess you will get the exact order in which you need to correct the picture
1) lens distortion correction if any, you should always make a mental note of how much is optimal so you don't have to waste time, this is the easiest step to go wrong
2) rotation correction if any
3) vertical perspective correction if any
usually you would not require much horizontal perspective correction for landscapes/wide scenes, unless you have done a very bad job when shooting; vertical perspecitve is the main thing - try not to do BOTH horizontal and vertical perspective correction, not sure if it works but i always end up with really screwed up results so i avoid it these days
please note that not all the time die die must correct distortion
or vertical perspective
or horizontal perspective
especially if you intend it as effect, artistic license is up to you
a rough guide when you are overdoing it is when people start commenting that the picture looks too weird, etc