Chris, the main thing with winter fishing is to choose the right species to fish for. For me the main 3 are pike, roach and chub. However, most species will feed, the hardest part is determining when these will feed.
Barbel for instance will come onto the feed during an increase in temperature, but, after a sustained temp. level, the fish become acclimatised and may be more willing to feed.
River fishing as far as I'm concerned is more prolific in winter than stillwater. This is because the fish have to feed more due to battling the current in running water.
Never go out thinking you'll bagup as this generally is a rarity unless you strike lucky and get on a hungry shoal. Leave your high protein baits like pellets and boilies at home, bread, worm and maggots are the best baits and deadbaits for pike. A smelly cheese paste is also a good bait to use and don't forget spicy/hot/garlicky flavourings for baits.
Sometimes roach and dace will feed right from the off, sometimes they don't turn on until later in the day. Its really a case of spending time on the water sussing out when the feeding spells are.
I'm quite sure other people on here will have other ideas, but these are just my own observations/tactics./forum/smilies/smile_smiley.gif