Absolutely nothing wrong with apps and dating sites. They're the new way of meeting people in a world that does everything online.
"Don’t go with the intention of pulling a girl - go with the intention of having fun, having some drinks etc" - disagree. If I think "I fancy going on the pull and going home with a little hottie" then that's exactly what I've done, with every intention of finding someone. Pulling girls is a game, and you need your head in it. If you just go out like "I'm gonna go out with my mates, drink, hopefully I end up talking to or dancing with someone but who knows" - never gonna happen.
"if you see a girl you like and you’re feeling confident, try to gauge if she has a boyfriend there with her, then just go up to her and give her a straight up compliment about her physical appearance with a confident smile and strong eye contact" - again, disagree. Every fool who tries approaching a girl and fails, started by going straight up and paying her compliments. Save the compliments for later when you're going in for the kill. Initially, just go up, make an excuse to talk to them ("my mates were boring me, so I walked off to mingle" always worked for me) and just chat to them, have a laugh and stuff. Your job at this point is to make them think "yeah, this guy is alright, not a creep or weirdo" so when you make your move, she already likes you and it's easier.
"when communicating with a girl at a bar/club ask her a cheeky/playfully arrogant question about yourself/your appearance to ensure you have some sort of approval from her." - if she has any sort of banter, she'll probably insult you (albeit playfully) if you do this. If she's a total airhead then she might just give you her approval like a teenage girl with a crush, but most likely not, most girls don't like to come across as easy or give away their attraction to you to soon.
Some decent advice in there, but as above, some I wholeheartedly disagree with.