• “How can I afford it?” Most really competitive PhD programs have assistantships that pay your tuition and living expenses.
• “Should I retake my GRE or TOEFL test?” Probably not enough time. If you think you have a good score, but you think it could be better, go ahead and apply. You can always retake the test next year and really focus on prepping for it.
• “What do I write in my Statement of Purpose?” Four things: 1) Why you want a PhD so bad that you are singing about it in the hallway, 2) what you will do with a PhD, 3) what specific topics or questions you’re interested in, and 4) why that school’s a great fit.
• “Who should write my recommendation letters?” Ask the best-known researchers you know in the field that you are applying. Next, ask anyone you’ve done research with. Third, ask whoever knows you best and will write these before the deadline.
• “How many schools should I apply to?” Since you’re doing this at the 11th hour, I’d limit yourself to three schools: Your dream school, your “best-fit” school, and a safety school. Otherwise, if you had lots of time, you might apply to as many as 10. (The third time I applied, I applied to 14). There are lots of tips on which schools to apply to here.
• “If I don’t get in to my dream school will it hurt my chance for next year?” Nope. They either won’t remember you applied (they might have 100+ applications), or they’ll think you’re persistent. And as someone once told me, "The P in Phd stands for 'Persistence.'"
With three weeks to go before the deadline, the most important part of your application is your Statement of Purpose. At this point, you can’t change your GPA, you can’t retake the GRE, and you can’t hang out at the mall hoping to make best friends with a Nobel Prize-winning recommendation letter writer.
What you can do is to write and rewrite your Statement of Purpose. Then have your recommenders give you comments on it. Many students are too shy to ask for this feedback, but it’s the most important thing you can do right now. I didn’t ask for feedback on my Statement the first time I applied, and I got into exactly -- hmmm -- zero PhD programs.
If after reading all of this, you’re still humming “Yo ho, yo ho, a PhD life for me,” take the plunge. Being an academic is a tremendously rich and rewarding calling. Pick three schools, apply, and when you hear back from them, we can talk about course corrections.
Good luck with a great career.