Lots of packing is the best thing. get a big sized box andfill it 1/3rd full of newspaper, bubble wrap or what ever packing you have, then put in your Amiga then fill the rest.
If you have a tower, then either remove all the cards and put them in antistatic bags pad them and send them seperatly (to the Amiga not to the box it is in!) or put lots of padding in the inside of the machine. But remember if you choose the latter to remove all the wadding BEFORE you switch your machine back on! :lol: