I have been playing RuneScape for some time already since. Well, for me, most of the time is spent on fishing and since I am a super fan of fishing, here is some tips that I would like to share.
First of all, fishing starts off with a simple small net that you can fish with. Usually at the start of training, it can get a little slow for all of you. Well you cannot expect much, can you? A few shrimps and anchovies is what you will get in the first 20 levels of your fishing career. They won't do much to your healing and they don't sell for much but you won't be facing them for long.
After hours of painstaking hard work of fishing for these shrimp-like creatures, it's time you changed your fishing gear to a fly fishing rod! This fishing rod will enable you to fish out some real fish! (not some shrimp-like creature) This time round, you would need some feathers in which you can buy from the fishing store at "Port Sarim". With your inventory stocked full of feathers and a fly fishing rod; it's time to head to Barbarian Village to fish out some Trout! This fish is easy to catch and heal some significant hp for beginners.
Okay, if you have read some guides, you would have known that you will be able to catch pike at level 25, but don't be fooled, this fish is hard to catch and thus you will be sitting in front of your computer doing nothing for some time.
At level 30, you will be able to fish some salmons! This fish, once again, is found in the same area as the Trout and easy to catch. Salmons heals significant hp for middle-range players and easy to cook. Be sure to bring along an axe this time to chop some trees down to make a fire for cooking. Your fishing level will skyrocket like never before!
At about level 35, some enthusiasts may want to fish the tuna since it's been some time you are at barbarian village, my advice to you is to NOT go for tuna as they are hard to catch and burns easily on the stove. Just bear with it and you may soon be able to achieve greater things.
What do I mean by greater things? At level 40, you will be able to fish some lobsters! Be sure to bring a set amount of money for the trip. It's very irritating to find that you have not enough money for the ship ride and you have to run all the way back to the nearest bank which is at Draynor Village to get your money. Also, make sure you changed your fishing gear this time round to a lobster pot, and this time round, no more irritating feathers, no more irritating axe, no more irritating logs and no more irritating fly fishing rod! All you need is your trustee lobster pot to earn first 100k!
At first, you may be tempted to try to cook your lobsters, well, sorry to break this to you but lobsters aren't meant for cooking. If you want to train your cooking, you have to raise you cooking up to at least level 60 before you stop burning them and you have to continue to cook salmons and trout, in which you may have become sick of. Also, raw lobsters are worth more on the market than cooked ones.
In addition to my tips, I would like to tell you that selling your lobsters to the general store on Karumja Island is a grave mistake. I once did it and regretted my actions. If you sold your lobsters to the shop keeper(s), you will only earn about 1k each time, if you sold them on the Grand Exchange, it can fetch a total of 8k per trip, which is about eight times the value. I once argued that running in between the island and the bank takes a long time. However, I have calculated before and this running at most only takes about five minutes or the time taken for half a inventory to be filled up with lobsters but you have to consider the fact that each full inventory sold on the Grand Exchange is eight times the value sold on the island. Thus my conclusion is to just deposit them in the bank and sell them all at once at the Grand Exchange.