The answer should depend on what type of student you are.
So are you a…
1. “Self-motivated, task-oriented”, science enthusiast?
Then every book on science fair projects was written for you – congrats! You can do almost any type of project you want, for example:
Plant projects – plant projects, by definition, show effort and effort is evaluated at judging. Plant projects should only be undertaken if you are this type of student because these projects require attention to detail, consistency, and a time commitment. The problem with many plant projects is that they lack creativity. There are only so many ways to water a plant, or grow a plant in different soil types, or under different conditions. See my tips on adding creativity under designing your own project.
Environmental projects – most environmental projects also require time and consequently, automatically show effort. Here again the challenge is creativity. Think about all the possible variables you could measure in the environment (temperature, salinity, humidity, sunlight, biomass, oxygen, pH, density, diversity, water content, etc.) and look for creative combinations in contrasting places or across gradients in time and/or space.
2. “Passionate about winning, but maybe not about science” competitor?
Unique projects – the key to a successful project for you is the “I’ve never seen that before” factor. The project does not need to take too long, but will need to be executed with proper scientific method, and must excel in the creativity category. The strategy is to be the project the judge has never seen before. Both the “start from scratch” and “making the project your own” strategies are successful, but there has to be a depth to the project (more than one experiment or more than one variable) to compete well.
3. “Might like science as long as the project is cool or the prize is cash” skeptic?
Cool projects – the key here is that the project will need to be “cool” (i.e. wicked, rad, sick, gnarly, whatever your generation’s term is) enough for you to complete and present it. Best options include: physics projects, or anything that uses bubble gum, spit-balls, paint balls, paper airplanes, catapults, radar guns, rockets, explosions, and/or something gross or scary (spiders, worms, mud, etc). These can be completed in one day, with options to expand and do more experiments if you like what you are doing.
4. “Desperately needs the extra credit for science class” student?
Just get it done projects – If this is you, that is OK. Your project needs to be quick and easy, because you probably also waited until the last minute, and perfectly complete (since it’s not going to be very creative). These are generally one day kitchen projects: boiling water, melting ice, or popping popcorn. Look at my list of projects of under “it’s due when ?!?!?”