How far do I need to cast to catch the fish, is a question I often hear!
Well you need to know where the food, shelter and fish are. Research the species your fishing for and look for areas where they may gather. Cod hunt closer to the shore at night, Bass will hunt for bait fish in really shallow water, Wrasse generally hang around close to rocks etc.
If you don’t know a fishing mark and you have two beach casters, or even 1 beach caster and a spinning rod take them both to the fishing mark, cast one as far as you can and plonk one in just 10 foot out into the sea. Then each cast with the long range rod cast less distance each time, and with the close rod cast a bit further each time covering the fishing ground until they meet. When this happens start again but cast to the left for the next set and so on until you have covered the seabed in search of you prize fish.