by Goldenzenith » Sun Sep 09, 2012 2:11 pm
Hi Ashun,
It's best when choosing projects to make a list of all the ones that seem interesting to you. What I would do is compile ideas from both Science Buddies and Google Scholar using the helpful links provided above by the other Experts. If you've decided that some are too expensive and others are too old, try to consider what parts could be changed in order for them to be more affordable or relevant in today's society.
Also, I'm not sure I quite understand your latest question. Are you asking whether you should do your experiment during the day, the afternoon, etc? That could be one variable to think about!
Need an idea or some inspiration?
http://www.sciencebuddies.org/science-fair-projects/project_ideas.shtml
Want to read up on awesome projects and science/math-related news?
http://www.sciencebuddies.org/blog/index.php
Enjoy!

-RM, Expert