Ohhh, bait, where do you start!!
Would probably be easier to make a list of stuff that doesn't catch fish, than to look at what does catch fish!!
But as already mentioned, no matter what it is, if you put it in the wrong place, you won't catch sod all!!
As a lot of people have mentioned, your best options with bait is to do something different from the rest, Sweetcorn, excellent allround bait but on numerous waters it has blown, add something different, such as a colour or flavour and it is a totally new bait again, the fact the corn contains betaine naturally will always make it a good catcher of fish, only problem is everyone is now using betaine!!
Hemp has always been a good catcher but that was sort of improved on by adding Chilli, yet again, slight change and off it goes again untill it gets hammered by everyone!
Boilies have become a norm and fish do recognise these as a natural food source, only problem is nobody really knows what actually goes into making boilies!! One company will sell a Low temp fishmeal boilie that will only contain 5% of normal fishmeal, try and prove otherwise, it would cost you thousands!
There are some excellent Boilies on the market at the moment, problem is there are also some awfull ones that probably cost the manufacturer less than £1 per kg to produce and will contain a high amount of semo and soya and not a lot else, you can test these by dropping them in a glass of water overnight and if they swell up loads and disintergrate with a small amount of pressure, then basically they are cheap!
Also the initial texture of a boilie is a dead give away, hard smotth boilies that take a fair bit of pressure to break are usually cheap, you can tell a good quality bait by the spongyness, a firm skin but nearly moist in the middle and will retain a certain amount of those traits after being in the water overnight!!
Be different, try slightly different things from the norm and don't follow the crowd, the going bait on the lake is normally down to one guy having a good session and then everyone jumping on the same bait, something out there will fish better if you put it in the right place!!