There is no right or wrong way to "undecorate" after the holidays. My method is to incorporate neutral winter type decor into my holiday decor, this way when I remove the glitz and all of the traditional colors I am left with cozy winter. I love that I don't have to re-decorate and pull out more stuff, it is already there for the winter season.
Think cozy, lots of fluffy pillows and throws in your living room area. Lots of candles and maybe even some twinkle lights around your home to maintain that amazing feeling of warmth during the holidays. My fave is snowy faux trees like these ones shown here.
In my breakfast nook area I left up one snowy garland with twinkle lights along with a tree. On the table all I did was remove a red stem from this arrangement of pine and pinecones. I don't do Valentines Day decor, so this look will carry me through February.
I love bringing my house plants back into view once the holiday decor is all put away. To me it evokes life and that Spring is literally right around the corner.