Hang a set of chimes outside your door or a bell. Ringing bells and chimes are said to ward off and dismiss negative energies. (Which is why we do so at the end of rituals, in some traditions) This will also dismiss any mischievous fairies, I'm told!
Place an upright (bristles up) broom near the entry to your home. Any spirits intent on harm will have to pass through the bristles in order to get to you and yours.
Place a bowl of magnetic oil charged water in your room to soak up the negativity. Float candles in it to make it a little less obvious and use black stones or black glass marbles to purify.
Place a witch's bottle filled with tacks, broken glass and ceramic, etc. behind your door where nobody can really see it. You can use a ceramic or colored glass bottle to make it less conspicuous.
Place amethyst near your door, or use something decorative with a bit of amethyst on it. Hanging an amethyst ring or cluster on a wreath or similar seasonal item makes your home more festive and helps keep
things focused and clear for you, as well.
Place a small guardian totem such as a dragon or gargoyle and explain its duties. People will just think you like statues of animals, usually.
You can inscribe a rune of protection into your doorway, or place a rune somewhere behind something, if you want to be secretive. Talismans such as the SATOR Square work well for this.
Place a dream catcher in your window to catch bad dreams before they come to you. Also try a broom under your bed, if you can't find a dream catcher. An athame placed between your mattresses will 'cut' the ties between yourself and old, bad dreams so they cannot come again.
If you can, buy a small goldfish bowl and a small fish. Fish are lucky in Asian mythology and bring wishes. It can never hurt to pamper a small animal for good karma!
Place a small element altar (make sure to use weather proof items) outside; a bowl to collect rain water for the birds, a chime to catch the breeze, a bird feeder and a candle to light in the evenings. (Catholic candles work well for this). An outdoor god or goddess statue will complete your altar.
Never allow a mirror to face or reflect a doorway or window. If yours does, move it if possible. If you cannot move it, use a SATOR square or similar protective talisman. Mirrors are doorways and should not be taken lightly in a witch's room.
Although hardly complete, these ideas should get you all started!