One of the best answers to that question probably resides right on your boat, tucked into a drawer or a locker, out of sight and mind. Those wonderful navigation charts we all use to get from point A to point B are actually secret treasure maps, revealing all the best fishing spots on the lake.

Fish are no different than people, in that they do things for specific reasons. They congregate at certain locations and avoid others altogether. Learn to read your navigational charts through a fish’s eyes and you can pinpoint all of the best spots on any body of water – including those you’ve never even been to before.

There’s a saying in fishing that 90 percent of the fish live in about 10 percent of the water. Biologists confirm this is absolutely true. So to put the odds in your favour next time you wet a line, you need to learn how to identify that magical 10 percent. Because no matter what you use for bait, you simply can’t catch a fish that isn’t there.

Charts help reveal that special 10 percent by showing the bottom depth plus a lot of other things like islands, shoreline points, submerged ridges, trenches, drop-offs and sunken islands, all of which represent housing to different species of fish. Your charts will also show places that have nothing to attract fish at all – those long, flat-bottomed, barren stretches where the lakebed looks like the bottom of a swimming pool. These spots don’t appeal to fish because they don’t offer places to hide. Fish congregate in spots where there’s stuff – rocks of various different sizes, weeds, steep drops, sunken humps. Not only can fish use these things to hide from predators, but as spots from which they themselves can ambush food. The more varied the bottom terrain, the more likely the spot will attract some kind of life.

Serious anglers have a language all their own, and they refer to these bottom features as structure. I like to define structure as any change to the bottom of a lake or river. Imagine you’re slowly trolling along a flat, featureless shoreline and then come upon an underwater point that juts out into the lake. Since that point represents a distinct change in the bottom of the lake, it's a form of structure. The same thing would apply if the bottom change was caused by a sunken reef, a steep drop-off or an underwater ridge that joins a couple of islands together.

Think of structure as the house that fish live in. The more houses in a given neighborhood, the more people who live there; the more structure in a given part of the lake, the more fish you’ll probably find. More fish in the neighborhood means you have a better chance of bringing home dinner.

So as you sit in the boat pondering your chart, look for areas where you see lots of stuff going on, lots of different forms of structure. Look for areas with lots of islands or depth changes. Places where points extend off the shore are good too, as are and submerged ridges or troughs connecting islands together, or connecting islands to the shore. If you fold the chart into quarters,  you can quickly identify the most promising looking spot in each corner of the lake. So right off the get-go, you have four good prospects. That’s where to point your bow.

To really stack the odds in your favour though, you can fine-tune your approach. Think of it as not just finding the fish’s house, but locating the actual dining room.

There’s another term fishermen use in conjunction with structure, and that’s cover. While structure refers to specific bottom features, cover describes the stuff on top of those features, like weeds, rocks, logs or sunken trees. If structure represents the fish’s house, then cover defines the different rooms. So when you arrive at your prospective spot, look for stuff on top of the structure that can provide fish with great hiding places and ambush spots. Depending on the depth, you can either spot this visually (polarized sunglasses really help) or search around with a depth finder.

Before you fire out that first cast though, remember that fish and people aren’t really very different in terms of behaviour. Watch a person walk up to a sofa and they never sit in the middle – they always sit on one end of the other. Fish are no different. Therefore, instead of casting right into the middle of a big patch of weeds, start on the ends. Chances are, that’s where most of the fish will be.

Take the same approach if you come to a shoal. Don’t look for the fish to hang around in the middle – find where the shoal ends, and concentrate your attention there. Sometimes, you can pick these places out on the chart before you even leave the dock.

So you’ve found some great structure and you’ve identified some promising-looking cover on top. To really fine-tune things, take a good look at the spot as you arrive and you can probably even figure out which way the fish are facing.

Waves can reveal a lot. Fish almost always face into currents, so if you have a strong current or some wind blowing onto your spot, you’ll want to cast along the windward side first. That is, the side facing the current or towards the breeze. Do so and you’ve not only found the fish’s house, but you’ve cast into the dining room and plunked your offering squarely on the fish’s plate.

If there’s no wind or current, then consider the angle of the sun. Unlike most boaters, fish don’t have sunglasses. They don’t even have eyelids. So look for them to hang out on the shady side of the cover. Would you stare into the sun all day if you didn’t really have to?

It’s true that 90 percent of the fish live in 10 percent of the water. With the help of a simply hydrographic chart, it’s not too difficult to identify the best spots on any lake or river. Once you’ve found the right neighborhood, it takes only a little basic observation to determine where the big ones are. Before you know it, you’ll be heading back to the dock with your dinner in the live well, and a newfound appreciation for your secret treasure maps.