Fishing Pond
Special thanks to RyanNope from the Zelda Dungeon forums for helping us write this guide!

It's 20 Rupees to fish as long as you like!
 - The Fishing Hole is found in the north-eastern area of Lake Hylia. As a child you can get to it as soon as you have access to Hyrule Field. As an adult you'll need the Hookshot and the Scarecrow's song or have beaten the Water Temple to raise the water level of the lake.
 - After paying 20 Rupees, you can fish for as long as you want, but you'll have to return the fishing rod when you leave, and pay again when you come back.

How To Fish
 - After getting the fishing pole from the Fishing Man, aim for the water and press B to cast. You can Z target the fish to aim directly at them, but you'll have to choose your distance by pressing A and the Control Stick in order to stop it in its tracks.

  A:    Reel line in.
  A + R:    Reel in faster.
  Z:    Zooms in and out.
  B:    Tugs the line (attracts fish).
  Control Stick:    Wiggles the line in a direction.

  Nothing:    Releases fish.
  A:    Reel line in / Sets the hook.
  Z:    Zooms in and out.
  Control Stick:    Pull line in direction.

Hold down A to nab a fish once it bites.

Press B and move the analog stick to attract fish!

Just don't move for a bit if you want the fish to let go.

Whatever you do, DON'T SCARE THE FISH!
 - The general idea is to Z target a fish, get in a good position, cast with B, then use A + Control Stick to stop the line before it gets too far. From there, (let it sink if you have the Sinking Lure,) reel it in slowly. When you get near your fish, use a combination of B and the Control Stick to wiggle your lure around. The best way is to wiggle a bit, stop, repeat. Think like a fish!
 - If another fish snags your line, just wait and it'll let go. If you miss your target fish or end up going too far, use A + R to reel in quickly and try again.

 - Once a fish nabs your lure (you can tell from the way it lunges at it, and if you have a Rumble Pack, it'll vibrate,) if it's the one you want, press A and pull back on the Control Stick to hook the line. After the hook has been set, the fish will show no mercy, so you shouldn't either. Keep holding A and use the Control Stick to pull the fish towards you. I find it helpful to aim towards the fish when it jumps in the water (to reel in more) then pull back when it's under water.
 - You can only hold one fish at a time, so hold onto one and keep trying until you're sure you have the biggest one around.

"That's A Real Lunker!"

Catch a big fish!

Get a Piece of a Heart!
 - The "biggest trick" to finding the "biggest fish" is to realize that each fish starts out in the same place (unless you catch it of course). As long as you don't jump in the water and scare them to the deep water, you can easily pick out specific fish.
 - That being said, the biggest fish can always be found near arched log, just a little towards the three poles sticking out of the water. Z target it once you find it, but be careful not to scare it away!
 - Also, the size of the fish tends to be a little larger than the "record fish" in the tank, so if the "biggest fish" was originally 15 pounds and you caught it, the next one would be around 18 pounds and so on.

The Prizes
Past: 10+ = Piece of a Heart
Future: 15+ = Golden Scale
Loach: Any = 50 Rupees

Tips & Tricks
1) DON'T SCARE THE FISH! They run to the deepest part of the pond if they get scared.
2)Whenever the fish jumps out of the water quickly release the A button and the Analog stick or the fish will get away.
3)You can use the Iron Boots to keep your feet down while you Z target your fish. You can also cast the line as long as your head is above the water.
4)Time can be a large factor in finding the bigger fish.

Frenzied Fish
 - Right before the sun sets and rises, little fish come out, causing all the others to go into a frenzy and chase after them. They're very easy to catch at this time. Once they've eaten a little fish, they'll calm down for about 30 seconds before starting up again. After a certain time, the little fish disappear and the frenzy stops.
 - Now, in some ways, this is the easiest time to fish, but in others, it's also the hardest. It's especially useful for catching the legendary Hylian Loach (see the section a little ways below). But, it's also INCREDIBLY hard to come at the perfect time when, not only are the fish frenzied, but the Loach is there.
 - Also, it's probably easier to find and catch the biggest fish the regular way, since the little ones won't get in the way and constantly snag your line that way.

The Sinking Lure
 - After catching a 10 pounder (past) or 15 pounds (future), you'll be able to find the Sinking Lure. It can be found in a few locations but you'll have to find it again every time you leave. It's invisible, so just walk around the following areas until you find it:

 - on the arched log.
 - next to the three rocks at the end of the feeder stream.
 - in the grass on the outside wall.

 - After you get it, catching the really big fish will become a sinch, as they love this thing. It's especially useful for catching the infamous, Hylian Loach (see below). But sadly all the fish you catch with it are deemed "illegal." Unless of course you say pretty please to the Fisherman.
 - You can keep the fish you catch with the Sinking Lure by talking with the fisherman and choosing "Let's talk about something." After that, go ahead and weigh your fish and he'll let you keep it.

Hylian Loach
 - This eel-like fish is very rare and weighs a lot! The prize for getting it is a measly 50 Rupees, but it sure does feel good to know you did it.
 - There's a 1 out of 4 chance that it will be in the lake each time you enter. If you're intending to catch it, it's best to enter, look for it, leave and try again if its not there. Once you've seen it, just get the rod, find the Sinking Lure and use the Iron Boots if you have them.

The Fisherman
 - As an adult you'll notice that the Fisherman is wearing a hat and a new rule has been posted that reads "4. Don't cast at anyone." Now, If you can cast at the Fisherman just right you'll snag his hat and pull it off his head, revealing that he's gone bald in the past 7 years. You can now either give it back, or throw it in the water for which he'll yell at you, then fine you 50 rupees. If you threw it in the water it'll be gone forever and every time you come back it'll still be gone. Now don't you feel bad?