For a special birthday or anniversary, decorate the room with enlargements of old photos of the guest of honour.
If the food you're preparing has a foreign theme, ask a travel agency, the local consulate or the tourist board of the appropriate country for posters and spread them as a tablecloth. Add little national flags to flower arrangements. Make the flower arrangements in the national colours, where possible.
If you forget to buy decorations, a plate of colourful fruits or unusual vegetables can make any table look festive.
For a children's party, how about an arrangement of stuffed animals or toys down the middle of the table? (The arrangement won't last long, of course.)
For help or ideas, look under 'Party goods' and 'Party planners and organisers' in the Yellow Pages.