I've posted in the past about fishing reservoirs on here:
Obviously as @yonny has said, find them.
Even though you have a nature reserve, that may not always be the best spot. I found that reservoir fish can really follow a good wind, and a big wind coming into my face is usually when I had my best catches.
A good shelter is a MUST; across a 100acres plus of water that wind can really blow, with big spray. I have had nights when rain and spray blew into my bivvy even well up the bank. Those were often the nights I caught most.
Reservoir fish can move very quickly. Baiting up on top of the fish can be enough to move them, but equally it could be enough to hold them if you bait up when they are not feeding. Also if they are not there, then you are giving them something to hold them if they move in while you are there.
My baiting to hold them tended to be Vitalin, mixed in with plenty of hemp, tigers and boilies. Bream attractor at times, but hookbaits were big, a 2x 20mm boilies, 20mm bottom and a 15mm pop-up as a snowman or a 20mm pop-up to reduce bream taking hookbaits.
I found that my catching depths were between 6 and 15feet deep, usually on a ledge rather than right out in the middle. The exceptions to fishing ledges were when I fished shallower bays, the shallower Dam at Wick Lane at Ardleigh and Alton Water culvert area, but they were still in those depth ranges.
The culvert at Alton was very snaggy, you could not fish directly onto it. It ate tackle, fragged mainline and hooklinks, blunted or broke hooks. You had to fish the swim to the left.
Feature finding is simple, but unless you have a brilliant memory, write it down; forget wraps as distances you write down, because water depth can change as water levels rise and fall.
Simply get your marker rod, cast out and check depths, features, feel the lead back. When I say feel the lead back, feel it at all times as you reel in. You might feel it lock up as you come back to the base of a ledge, or you might find blocks or other lumps on the bottom.
If you count and let the float up, be aware that there may be undertow, so you could be a few metres away from the actual lead.
Check each swim like a clock.
Alton between highest and lowest level was a 4metre straight vertical height on the bridge supports at Lemons Hill. That could equate to water level being 10metres (!) down the bank.