Fish finders are the greatest invention for fishing, as long as you have it set up properly. Unfortunately, most anglers haven't and think they are good to go out of the box. But there are a few thing you should do before you hit the water fishing.

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Now this is a very broad topic to cover, but I'll try and narrow it down to the three most popular kinds of fishing - offshore, estuaries and inland lakes.

Let's start off with offshore fishing and a couple of small tweaks that you can do to your unit that will help you zone in on the fish. Nowadays, the fish finders have chirp frequency built into the unit -but what is that?

Conventional fish finders used a single or dual-frequency transducer that had a range of frequencies where you had to chose one or the other. Now, with the introduction of chirp in nearly every brand on the market, our flexibility with transducers really widens.

Basically, there are three types of chirp which are low, medium or high chirp. In these chirp frequencies, it is a sweep of a range of different ones that give greater target separation and better depth perception, making the image a hell of a lot clearer than older models. For instance, an Airmar tm260 transducer will run at 50khz and has a beam width of 19 degrees. At 19 degrees, it will have a beam width of 100m diameter and can read up to 790m of water.

Nowadays, a dual-frequency chirp transducer such as the TM275LHW which gives you the best of both worlds when it comes to shallow and deep water usage. This is fast becoming our most popular transducer to fit out due to the fact you basically get two transducers in one with no need for a sonar box in most instances.

These transducers use 42-65khz in the lower frequency setting and from 150-250khz in the high frequency. The W in the model number means that it is a wide-angled transducer, making it cover more water at one time. The difference in area from a basic low chirp transducer and the wide angle is about 30-odd metres, which can mean the difference between finding that structure or not. The TM275LHW has a max depth reading of a whopping 900m in right conditions.

As I mentioned before, this transducer can also do all your shallow water usage on the high setting. One of the things we see frequently by anglers who have just fired up their new unit is they haven't taken the time to read the manual.

There's a lot of information in these manuals so you can have your unit pretty much set up before you get out on the water. Garmin units are pretty much set to go as soon as you get them out of the box, and with a couple of minor tweaks once you're on the water they are reading fish in no time.

When it comes to estuaries and lakes, a lot of the same settings can be used due to the similarity in depth of water. The major difference will be the water clarity or interference that is typically shown on the units.

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Normally, estuaries are a lot dirtier then lakes, so simply turning the surface clarity down or the interference up will increase the picture quality and make the return better on the screen. Unless the water is chocolate colour, I won't set mine on more then half of what the scale is on the particular unit. The other feature - and one that people struggle to get their head around - is the "side vu", or structure scan, and what they are actually looking at. This great feature allows you to scan left and right of the boat without driving directly over the fish that you mark. I use mine to find structure more then fish, especially in the bigger areas such as flats.

Remember that once you sound something you like on it, drop a waypoint so that you can return back and fish directly on that structure or fish schools. One thing that you will see on your fish finder coming into winter, once the water becomes dirty, is the thermocline where the saltwater and freshwater meet. This is a very important piece of info when targeting fish over winter, as they will sit below this line as that is where the oxygen is.

If I fish lakes, then I tend to run side vu and down vu on a combo screen, as sonar can be a bit hard to determine weed from fish. The down vu just takes the guess work out of it. You can actually see the weed shape and the tree branches on down vu opposed to sonar that will look like a line of fish coming from the bottom.

If you're trolling, then simply put your ping speed up which will increase the signals coming back and forth from the transducer and the objects you're sounding up.

How do you know when your gain or sensitivity is right on fish finders?

This is a fairly broad topic, but a simple explanation is if you're reading arches and still a bit of clutter, then it's fairly well spot on.

If you turn it down too much you'll pick up bigger returns but will struggle to find the bait, which is usually a big part of finding the predators.

Hope this sheds some light on what you should look for, and gives you a couple little hints and tricks for getting the best out of your unit.