There's also the somewhat counterintuitive idea of "be bold; start cold". Basically, once you get hiking, you'll get a lot warmer, so you might as well start a little chilly and save yourself getting sweaty 20 minutes in and having to take off a layer.

Better yet understand that none of your gear makes heat, you do. Think of your sleeping bag and clothes as batteries that need to be recharged periodically and your body is a generator. When you shiver that is your body trying to burn calories to produce heat. You can stay much warmer by keeping busy and moving around than you will by standing around a fire. When you wake up cold in the middle of the night, move your legs like you're riding a bicycle while laying on your side. It won't take long to warm up. Also keep an isolating layer between you and the ground like a foam sleeping pad. It also works for when standing on frozen ground.

I used to drag my clothes into bed with me in winter when I was a kid. No central heating, no double glazing, no insulation, no carpets. Might as well have been living in a tent.

To combat this you can fill a heat tolerant water bottle with some boiled water, wrap it in a shirt or sweater to prevent burning, and put it into your sleeping bag to warm it up quickly.

The first time I did this I ended up so hot that I had to take it out. Its a wonderful trick and I have woken up spooning the cool water bottle in the morning