division_9 :
1) Apply the best thermal paste you can(i.e. IC diamond or Arctic MX-4 etc)
2) Don't leave the battery plugged in while running off a wall outlet as it'll wear your battery to half capacity in no time(unless you need to use the battery as a UIPS/power outage protection).
3) If your laptop has a glossy screen I'd suggest a "Screen protector" so your nice shiny screen doesn't become a fingerprint magnet.
1)not exactly a must unless it heats up unnaturally. even then, as jaguarskx mentioned, this will void your warranty.
2)true for older laptops with nickel based batteries. not so much for modern laptops with Lithium-Ion batteries:
http://www.dansdata.com/danletters017.htm
http://www.marco.org/2009/09/24/laptop-battery-myths
http://www.huffingtonpost.com/2012/08/31/9-biggest-tech-myths-busted_n_1840745.html#slide=1435423
(no.4 and no.5 and it's corresponding links on the slideshow should be of interest)
my own personal experience at this by plugging my laptop in most of the time with the battery showed only a 5 minute decrease in battery life over it's initial 5.5 hours within the year. i compared this with my boss' laptop which he also bought last year and constantly unplugs it. it now only lasts for 20-30 minutes on battery over it's initial battery life of 6-7 hours.
3)not exactly relevant in maintaining a laptop's lifespan unless he/she constantly touches the screen or it's constantly vulnerable to scratches, say, from a cat.
generally, outside of the common PC maintenance (defrag, virus scans, etc.), the only thing you can do is not to drop it or experience any sort of physical shock, naturally. if you're prone to that or are paranoid of that happening, well, there's always buying for the sake of build quality, expensive as it is. i.e; i have a $2.5K Asus notebook from 2003, that's still running fine today. heats up like hell, had a drink fell on the keyboard once, fell 2-3 feet to the ground 3 times, got slammed between a door once, (i was a very careless college student) and the only problems with it now is that the HDD gets disconnected if i move it too much due to a design flaw (HDD compartment is too big), the hinge on the screen snapped off due to some melted glue, and the 10-15 minutes battery life. i've only ever send it out for repair once. still works well as a desktop replacement for general use.