Do yourself a favour, read this before heading offshore
THE set-up for deep sea fishing is as important as learning to fish the ocean.
Boats need to be safe and equipment needs to be right for the type of fishing you are about to undertake.
Safety first: Offshore boats have special requirements depending on how far you are planning on going. Regardless of the legal requirements I believe any boat heading offshore should carry the basics of a marine radio, EPIRB, flares, v sheet, PFD 1 lifejackets, first aid kit, mobile phone and some form of survival kit containing food and water. All vessels should log in with Marine Rescue (UHF 88, VHF 16) with details of where they going, how long for as well as boat and contact details. This takes less than a minute of your time.
Equipment: there is a huge amount of electrical equipment you can buy to help you navigate and then find fish. Like most things in life the more you spend the better it gets. Try not to be too stingy in this regard; good equipment does make a difference.
GPS: these units have been readily available to the public since the 1980s and get better every model. They will allow you to travel to a spot in a direct line saving fuel and time as well as record all your spots for future trips. Almost all GPS units will allow you to store around 1000 spots. Save anything that looks good, (the fish may not be biting at that spot today but they were there). I have found fish come back to the same areas annually. So I mark spots with the date and what I caught (eg. 25.5.15snap.) this creates a diary in your GPS, they may not be exactly there next time but they will be within 100m as a general rule.
Sounders/sonar: most sounders now come with dual transducers (high and low frequency) - seems back to front but you should use high in the shallow water and low in the deep water. Most people fish in less than 50m of water, so high is all you would use. Low comes into its own when we fish 100 to 900m deep. The basic auto command on most sounders will let you find structure and fish. If you have fish ID and fish alarm my advice is turn them off. They will just confuse you and are far from accurate.
Have the sounder in full screen mode when travelling but change to a split screen with a zoom box set at around 7 to 10m when looking for fish.
Tweak your sounder, turn the chart speed up to 75% or faster, this will give you a more accurate vision of the change in the bottom structure as you travel over it. Turn the sensitivity up to 80% or better, depending on the amount of noise it picks up. This will show fish on the edge of you transducer limit better. Travel as slow as you can in circles around a spot and when you locate fish mark with the gps.