Currently, I am a sophomore in high school. In my freshman year my GPA has not been great being 3.15. However, my current grades are low A’s an I am taking one AP class. If I do great in my Junior and Senior year and get straight A’s, would I have any chance at getting into Caltech and if so, how should I raise those chances?
Extracurriculars matter more than you think.
Get a ridiculously high score on the SAT, and STEM related SAT IIs.
Do exactly what you just said: study like you’ve never studied before. If you want Caltech that badly, you’ll find a way.
Once you start writing your essay, get multiple people to go over it. One of them should be your English teacher.
This is assuming you want Caltech more than you’ve ever wanted anything before. Because that’s what it’ll take.
Good luck. 
Probably not it only has 250 or so spots in the freshman class
You need a near perfect SAT/ACT and perfect GPA and intuitive thinking.
You need extracurriculars that matter to you with more quality vs. quantity.
You need to have shown leadership in various sports and clubs.
@above maybe you mistyped but you don’t need a perfect GPA — you need a “close-to-perfect” GPA, sure, but clearly not everyone who got in had a 4.0
For Caltech, you need to really understand the subjects you are taking, not just do enough to get an A. A lot of outside reading about science would be valuable. (In my opinion, it would be more valuable than leadership, as far as Caltech is concerned, though leadership is highly valued almost everywhere.) Look at the AOPS math web site, and work on their problems. If your school offers math contests, you should participate in them. It would be a really good idea to look at old contest exams on the AMC web site. At first, you may not score well on them. However, if you think hard about the questions, as time goes on, your scores should keep rising. It would be a good idea to look at some of the books Richard Feynman has written. You can read college science texts after you have had the corresponding course in high school (i.e., college chemistry after high school chemistry . . . ). You probably have not taken high school physics yet. I recommend the PSSC high school physics textbook, to go along with your high school book, if it is not PSSC. You can read books in number theory now. When you study geometry, take a look at non-Euclidean geometry. Subscriptions to Scientific American and Science would be a good idea.
If these things excite you, and you find them fascinating, then Caltech may well be for you, and your freshman GPA will become irrelevant. If you don’t really like them, you probably will not like Caltech either.
Getting involved in scientific research would also be a good idea, if you have a college or university near you. It will be more meaningful if you acquire some additional background knowledge first, though.
@QuantMech Thanks for the explanation. Ill be sure to look into the resources you have listed