Line is the thing that seperates you from the fish. It is often the weak point in anglers tackle. Line strength is rated in pounds, but remember that though a fish may weigh ten lbs, it will struggle, so exert more pressure on the line. My general choice for shore fishing is about 20lb line, but you should use 25-30lb line if fishing on snaggy ground. You only need about 10lb line when spinning.
Anglers often use a shock leader in the intrest of safety.
It is basically a length of line of about 15-30 feet which is heavier than the mainline. I would suggest you use one of about 50lb breaking strain. If you buy sub-standard swivels, for example, they might break, and you will lose all of your gear. Try and buy tackle ffrom good quality names such as Mustad or Breakaway, the few pence extra may pay of in the end.