Hints for coaching Experimental Design:
1) Scan middle school textbooks for definitions and topics that might show up in a tournament. If the kids don't know what buoyancy or period of a pendulum is, they won't be able to design an event for it.
2) Look at books for simple elementary and middle school experiments, just to know what's out there. Dorling Kindersley and Usborne books come to mind as well as books by Janice VanCleave.
3) A coach can help identify the threesome's strengths. Who is good at making a graph? Who is good at writing quickly, legibily and with passable spelling? Who is adept at running experiments accurately and measuring? Each student should know his or her own role and always perform the same role (unless coach says to change...) Each of the three students should be busy all the time!
4) Students MUST understand that they should have exactly one IV, one DV, and know what both are measuring. All three should be decent at coming up with a simple experiment given a topic and pile of materials. Practice this! Give them some random materials and a topic and all three should be able to come up with "IV is height of ramp measured in cm and DV is distance car travels beyond ramp end measured in cm." For a practice, each student must memorize the current IV, DV, and units for each. I've read some write ups where students start with the IV being mass in grams and soon the IV morphs into density. Yikes. Everything (hypothesis, experiment, data table, graph, labels, evaluation) must refer to the same IV and DV. I've also read write ups where a young middle schooler is trying to get all fancy with TWO DVs. Nope, just one DV.
5) Be sure that figures, illustrations, tables, and graphs are properly labeled. It's silly to lose points on a forgotten label, unit, etc.
6) Scan the internet for experimental design scenarios that have been used at past tournaments. Every now and then, a team will show up at tournament and discover that they recently practiced something very similar if not identical!
Good luck,
Kelly