Daniel,
First you will need to try and locate the feeding areas of the resident fish. You could try asking the regulars or spend some time lookig for signs of feeding fish, such as extra colour in the water or the tiny bubbles (fizz) that tench produce when feeding.
At first try using small general baits such as castor, maggot or worm first. When you have got them feeding on this try using more selective baits such as sweetcorn or bread flake on the hook. If you are able to catch one or two fish using these baits then you will be able to fish these throughout your session,both on the hook and as loosefeed. Holpefully this would result in catching a larger size of fish.
Best of luck
Jason