There's a lot of luck involved when it comes to catching fish in the sea, mainly because it is just so big and finding the fish without a fish finder requires local knowledge and being in the right place at the right time. If that wasn't difficult enough then you need to be using the correct bait and setting your fishing tackle for the right conditions.
If you are lucky enough to be in the right place at the right time and the fish are leaping all round you then make sure that you tackle up correctly. If you are floating 8 feet from the bottom and the fish are feeding on the bottom, then despite the fact that there are hungry fish down there just itching to steal your bait, you'll never no about it! because your bait is just too far away from where they are feeding. Like wise if you tie a heavy weight to your line and chuck it out, you could find that all you end up doing is winding in your line every half hour only to find the bait stripped because the weight tied to your line was preventing the bite from being detected.
I can also assure you that watching a 12 year old 75 yards down the way from you pulling them in as if there's no tomorrow with a cheap £10 rod & reel can be a depressing experience!
The Bad News - There are hundreds of pages written on the many ways to set up your fishing tackle and there equally as many fancy names for setting up rigs and fishing gear which (Now the good news) I am not going to delve into. Instead I am going to stick with a handful of my favourite set ups which have struck gold where ever I've been lucky enough to fish.
1) Tying the hook onto your line. Once you've mastered this technique you will never use another method. Slightly tricky to get right but super strong knot and easy to undo if you need to. Also tricky to explain! First thread your line through the hook and leave a small loop near the top of the hook. Then loop the excess line round the main line (approx 4 - 6 loops). Push the line through the small loop you made at the top of the hook and then hold the line you pushed though the loop and pull on the main line and you should see the knot start to tighten as in fig 2 of the picture below. Pull tight until the knot is firm (You can also grip the knot and slide it towards the hook whilst pulling on the main line) and cut of any excess line that is left over. If you can't master this then don't fret. Just use a good old fashion granny knot. As long as you don't have to much excess line near the hook and it doesn't come loose then you've done the job.

This
has to be my favourite set up because its easy to do and you can start fishing
within minutes of arriving at your destination. As shown in the picture this set
up requires 2 swivels, 1 weight (varies dependant on current) and a hook. The
swivels are used for three purposes. One to stop the weight racing back up the
line, two to stop the weight from sliding down to the hook and three to allow
the line to twist freely without actually twisting the fishing line.
Cut of about 2 feet of line (you can experiment with length) and another piece about 1 foot long. tie the first swivel on to your main line then tie the 1 foot piece of line to the other end of the swivel. Thread your weight through the 1 foot section of line and then attach the 2nd swivel. Tie the 2 foot section of line on to the swivel and then tie your hook on the end of the line and you are done. Why is this effective? When a fish bites, the line can pass freely through the weight to the end of you rod allowing you to detect even the slightest of bites because the fish is not pulling the weight as well as the bait. Plus the bait will move freely with the tide giving it a more natural appearance.