Usually it takes about 40 observations to be able to state any result with a reasonable amount of certainty. So if you're testing seed-size preference in ants, you'll want to run at least 40 tests where you offer seed choices to ants. Try to ask questions that you can answer by counting things. Not only does this make collecting the data easier, but it allows you to present your information in charts and graphs. You can even run simple statistical analyses to determine whether your results differ significantly from what would normally be expected.
Science takes time.
What seems like a simple question might end up taking a week or more to study. Or it might grow into a three year project. However long it takes, don't rush through it. You need time to read and digest information, to test things and re-adjust your experiment. Talk over your projects with other people, view it from different angles.