Ok thanks its a single speed bike.
Well in that case, it deserves extra special care....
Get a suitable bike box from a bike shop then -
Leave the rear wheel in the frame, take the pedals off, remove the front wheel and slacken off the stem to allow the bars to turn in line with the frame (ie through 90 degrees) Remove saddle and post.
Put a spacer between the fork dropouts (either the plastic ones - blag one from your bike shop when you get the box) or a piece of wood cut to 100mm and taped in place.
Cover frame tubes in pipe insulation and/or bubble wrap, paying special attention to the head tube, BB shell and fork dropouts. Put extra padding in the form of cardboard around these when you fit the bike in the box.
Wrap and pad all the extra stuff (front wheel, pedals, saddle and post) and fit these in the box, front wheel alongside the frame with extra cardboard over the ends of the spindle (remove the skewer). Make sure that all the loose items can't move around if the box is turned upside down so tape them either to the box or to the frame. Add as much bubble wrap, cardboard or polystyrene as you feel is necessary.
If the box you get is bigger than you need, then modify it to fit more snugly.
Tape everything up really well but leave the handling holes clear - if the box is easy to handle it's less likely to get abused.
Write "DO NOT LAY FLAT" in big black marker pen on both sides.
Print out an address label (make it big and clear) and tape it to the box with clear tape right over the whole label. Do another with the senders details.
Insure it adequately