It's all over the web, someone has come up with a great idea for a simple to make but effective wasp trap , that doesn't cost anything to build. And here's the instructions, culled from the best of the online articles. 

1. Take an empty plastic bottle; a mineral water bottle will do just fine.
2. Cut the top off, just where the diameter has become as wide as the body.
3. The base of the bottle looks like a jar with a wide opening.
4. Fill the base partially full of wasp  bait.

   Late Winter and Spring:

   Use hamburger meat or luncheon meat. The macho wasps are attracted to protein during their mating season.

   Summer and Fall

   Use a sweet substance: Soda Pop, jam, honey dew melon rind, crushed grapes or a piece of fruit, molasses, vodka and orange.

5. To add to the killing power of the trap, add some sweet liquid, such as sugar water or lemonade along with some soapy detergent or a tablespoon of laundry soap.
6. Invert the top of the plastic bottle, which should look like a funnel, and place it inside the lower half of the bottle, remember to remove the plastic top.
7. It should hold in place, depending on the bottle shape
8. Make sure the interior fluid level does not reach to the lip of the funnel
9. Seal the edges if there is not a good contact all the way round, using tape, gum, leaves, staples, whatever is most appropriate
10. Cut two holes in the plastic where the two pieces come together, near the top. Put string through the holes and use it to hang the bottle.
11. Pour hot soapy water, dishwashing soap or Vaseliine into the exposed funnel, as this will cause the wasps to lose their footing and fall into the trap
12. Place in an area where not too many people walk
13. The trap works best at a height of four feet
14. The trap works best at around 85 degrees
15. The wasps  will fly in, attracted to the sweet. When they try and leave, wasp logic dictates they should look for the highest point to exit. They will fly around, but miss the inverted opening. When they get tired they will fall into the soapy liquid. The liquid, will stick to the wasps body making it impossible for them to breath.
16. Empty the trap regularly making sure the wasps are dead.
17. Replenish the bait every few days.
18. Don't let live wasps  escape as they can bring an angry swarm of wasps. Don't crush wasp bodies as that emits a smell warning the wasps. Kill the wasps with water, or freeze them. You can also free the wasps in the wild, however they may return 
19. Bury dead wasps  or flush them down the toilet as the dead wasps emit a warning odor to living wasps.

    Good luck and enjoy your outdoor picnics in safety. 
    This tip brought to you by A # 1 Pest Control