One thing I like about World of Warcraft is something I liked about Runescape as well - there are a billion skills that one can advance within any one toon, at any one time.
I like variety in my play. I like being able to go out and slaughter unintelligent things, but I also like to PvP periodically, pitting myself up against PvP vets and newbies alike.
Sometimes I can't pay a great lot of attention to what I'm doing, and that's when I'll go out and farm leather or park at a river to fish, or run down the shore of the ocean mounting and dismounting regularly in order to find and fish the schools that have spawned there.
I really like how fishing and cooking and fighting all tie in together, as well - the fish get cooked and provide the temporary buffs to my toons which allows them to survive better and longer in both solo and grouped situations. (this was something I couldn't be bothered with my first time through on my first toon, the 10-15 min buffs were too short, but now I can pay attention to more things and the buffs get applied at strategic times)
At any rate... I noticed that my 40s Mage had a higher fishing level than my late-50s Warrior, so while I was waiting on a friend's phone call, I started doing some serious fishing with my Warrior.
Addon Assistance
I've had the addon "Fishing Buddy" for ages, and have upgraded it countless times due to patches that broke its functionality. It's been recording my fishing results for probably about a year, if not more, so it's got some decent results.
I haven't done much in the way of "strategic fishing", however - my first toon through the Fishing levels did it more to feed her pet than to feed herself, so the 'buff fish' weren't focussed on very much. I've only started to do that recently.
The picture to the left is the graphical representation of the "Seasonal" and "Day/Night" fish that I've fished since it began tracking that type of information (could very well be from the beginning of all my Fishing Buddy use). Not much detail is there yet, but I plan to do some specific fishing to get that graph populated better over the next while.
The fish represented cook up into Nightfin Soup
Requires Level 35
Use: Restores 874 health over 27 seconds. Must remain seated while eating. Also restores 8 Mana every 5 seconds for 10 minutes.
Item display is courtesy world of warcraft.allakhazam.com. ',VAUTO,HAUTO,FULLHTML);" onmouseout="return nd();">Nightfin Soup (good for casters), Poached Sunscale Salmon
Requires Level 35
Use: Restores 874 health over 27 seconds. Must remain seated while eating. Also restores 6 health every 5 seconds for 10 minutes.
Item display is courtesy world of warcraft.allakhazam.com. ',VAUTO,HAUTO,FULLHTML);" onmouseout="return nd();">Poached Sunscale Salmon (good for tanks/soloing), Grilled Squid
Requires Level 35
Use: Restores 874 health over 27 seconds. Must remain seated while eating. If you eat for 10 seconds will also increase your Agility by 10 for 10 minutes.
Item display is courtesy world of warcraft.allakhazam.com. ',VAUTO,HAUTO,FULLHTML);" onmouseout="return nd();">Grilled Squid (good for Hunters, Rogues), Hot Smoked Bass
Requires Level 35
Use: Restores 874 health over 27 seconds. Must remain seated while eating. Also increases your Spirit by 10 for 10 minutes.
Item display is courtesy world of warcraft.allakhazam.com. ',VAUTO,HAUTO,FULLHTML);" onmouseout="return nd();">Hot Smoked Bass (good for practically nothing).
And of course, even if you don't use them yourself, the raw fishes can be sold on the Auction House, and things like raw Nightfins can be quite lucrative due to their scarcity and buffing effects.