Ok 1st off buy:small net, fishing rod, fly fishing rod, harpoon, lobster pot,fishing bait (2000) and feathers (2500).
2nd:go fish srimps until level 5 and then go fish sardine using fishing rod until 25 (you will start cathicng herring at level 10)(you can find the sardine spot at dragnor villiage)
3rd: go fish trout using fly road in lumbridge river near the collapesed mine until level 30
4th:now time for tuna go to karamja fishing spot and harrpon tuna until 41
5th: now fish lobster and wow all of a sudden you have 41 fishing!

i used this and i now have 55 fishing look me up on high scores (it may look rubbish but i have only played 1 month)