Effects of Winter[]
Winter comes with force in TFC, but first, what is your Z coordinate?
If it's anything between -6000 and 6000 then Winter probably won't happen for you (open to see by pressing f3 or fn+f3 for macs). That's because of the equator. The actual equator is located at 0, and if you're there then it's likely your crops won't even die. Coordinates of about -8000 and up tend to be just classed at the level where Winter can become a pain, and in levels of about -15000+ then you're looking at being snowed in.
The main danger of Winter is that all your crops will freeze and die. This means food will become hard to come by, and eventually be fatal. Snow will also slow you down considerably, and unless you can craft snowshoes then it will be hard to travel far. Fruit will no longer come from trees and bushes, and some young animals will no longer grow.
Preparations[]
The main piece of advice I'd give to be prepared is to stock up on food, and depending on where you are, make sure that you have plenty of water in case you can't get to your water supply.
Food[]
Lots. Try to keep a variety, or your max health will go down.
Water[]
Try to have at least four ceramic jugs with you at all times, filled with fresh water.