Best method by far is the feeder, and maggots. For other species, fish dawn to dusk with worms - fat lobworms will catch any of the largher species.
But if you want to know what's in there, the best way of all is to look. Yes, a good pair of polaroids and a few hours wandering the bank will uncover most of what you need to know, especially if you can find a tree and climb it.
The art of looking for fish seems to have been forgotten....
one word of warning, branches over hanging the lake do some times break. depositing you waist deep in thick stinking mud and knackering your binoculars.
but you will see much more if you are up a tree for a couple of days.
Take your rod and plummet and have a look around for features.
If you prefer to float fish look for marginal shelves and reed beds.
Fish on the bottom to start and go from there.