A lot of it is water dependent but on the water I fish:
Location is always the most important bit but in winter more so as they're far more tricky to find. As we head into Autumn and temps drop they'll stop showing in the day and start showing at night, this is normally near where they'll end up for winter. Areas near (not in) the deepest water and central areas are worth keeping an eye on. Do a couple of nights when the temps start to drop and you should see/hear them if you're prepared to stay up late (very late in some cases).
As soon as you think you know where they'll end up start putting a bit of bait in. Don't leave it too late as once they shut up shop for winter there's no getting them going again unless you get some seriously good conditions. If you can get the bait in before they shut up shop you can keep them going right through winter with consistent light baiting.
Tactics/rigs etc are not that important imo, just don't go crazy with bait. The important bit is being on them and keeping them going with a little bait in the right area.
Don't ignore zigs. Even if you keep them going with bait they'll likely only feed for an hour a day so zigs can increase your chances, especially during the day, significantly.
For clothing, the Snugpak stuff was a massive game changer for me. SJ6 or SJ9 jacket and Sleeka salopettes are the ones. It's like wearing a sleeping bag, you can get away with just a T-shirt underneath. That Quantum winter suit is no good, it'll protect you from the wind but that's about it. DO NOT skimp on the clothing, spend proper money on proper gear (most fishing branded stuff is not what I consider to be proper winter gear). A decent sleeping bag is obviously a must of you do decide to do nights.
Take plenty of tea.