Just one (or ten) more points. First, don't over
excercise. I know it sounds obvious, but I mean
it...
If you over strain yourself, you may end up tearing your ligiments.
Unlike muscles, ligiments don't heal themselves very well. Over
time, if you seriously wear out your ligiments, you will experience
considerable pain when you use your joints. Most importantly, watch
out for your knees. In particular, I advise against doing too many
"squat"-type excercises (bad for knees).
Don't do weights everyday. Your body needs time to
recover! 3 times a week should be more than enough.
Instrestingly, I've found out - the hard way - that having enough
sleep is also important to gaining weight. Don't be the type of
loser who stays up till 3 am playing computer games (like me last
year). Even if you eat till you think you'll die, and excercise
till you can't even stand, you won't gain much mass if you don't
let your body REST.
BTW, I'm also 180+ cm.... 183 cm, in fact. Last year I was a measly
56kg (really skinny, I know!). Now, I'm 70 kg. 
The best way for skinny guys to look good in shirts/swimming
trunks/birthday suit/whatever? Gain weight!!!
P.S. I drank so much milk trying to gain weight that the
colour of my sh*t actually
changed!!! Trust me, I'm not sh*tting you! (pun not
intended) It was... cool. 
