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@cowgirlsdontcry You're on point about grading too hard on APA style. As much as I personally dislike it, at least half of the points for assignments are APA formatting. My rubric states I need to take off 1 point per mistake. Students, of course, find it very unfair, but I can't change the rubric a professor gives me. I think it has to do with the class being Research Methods. So the point is for students to understand the writing style standard in the psychology field.

I'm an international student who goes by a different name in the US. In fact at this point being called by my real name is confusing and there has been a time that someone called me by my real name and I started speaking in my native language. When people find out that I go by a nickname, they try to be nice and always ask what my real name is, and then I try to teach them, and they mispronounce it (I don't blame them) and get upset that they can't pronounce it right. I don't mind being called something else, and I'm not always in the mood to teach people how to say my real name right. So calling this student "Leo" is totally fine.
I also don't think it's insensitive or rude to demand an English or anglicized name from someone. No one is obligated to spend time getting your (or mine) name right.

So, here's my advice from my experience 2 years ago when I was in your shoes and applying to Clinical Psych Ph.D. programs. I applied to 10 sites, got 6 interviews, and got into my top choice. This advice isn't a "hard-and-fast" guide for everyone, even in clinical, but I think these tips are helpful (even if they've been stated before).
 
For phone interviews:
Honestly, I dressed pretty casually for these because I personally wanted to feel comfortable. Some will say dress for success. You do you, honestly.  Be in an area, like a bedroom, where there is minimal background noise. I also advice to use a good pair of headphones with a mic, if possible.  Have a note pad and pen to take notes from the conversation. At the top of the note pad, write down before the interview at least 2-3 questions that you have, as well as anything else you think is relevant.  Speak calmly, and take a breath before you answer the phone.   
Skype interviews:
Wear at least business casual. I actually usually wore a suit (I am a male, so that's a wide difference honestly).  Again, I'd advise to skype in your room or somewhere that is quiet. If your room doesn't work, I advise finding a quiet place at work or a library in a private room.  Again, wearing headphones can help with quality of your speech/hearing your interviewer.  Same rules of notepad and pen apply as before.  Look at the camera lens, not at yourself or the PI on the screen. Looking at the camera feels weird, but it means you are making eye contact.   
In-person interviews
The agendas for campus interviews vary WIDELY. Some places will be a short day of interviews with a handful of people; other sites will have 2-3 day extravaganzas with parties, interviews, campus tours, etc. Plan your wardrobe accordingly. Unless stated otherwise, you should be in business formal for all of the interviews, and business casual for all of the dinners/parties.  At the parties/socials, DO NOT (and I mean this) get drunk or out of control. That's pretty much an immediate ax from the committee. Generally speaking, just have a few drinks if you'd like (or don't... nobody cares), and socialize with current students, other applicants, PIs, etc. BE NICE!!! It often helps, especially with other applicants, to talk about pleasantries and stuff going on, as well as shared interests OUTSIDE of psychology. Nobody wants to get into a metaphorical d*ck waving contest with you, and the grad students interviewing you, especially, will not look favorably on that.  This goes with the above, but if you are staying with a host or really whenever you are interacting with grad students, you should be on your best behavior. You should be polite and respectful of your host student's home, and it is often nice to bring a small gift from where you are (less than $5) and a thank you card. While you should and can ask candid questions about life as a grad student, the culture of the city/university, faculty-student dynamics, etc., you should probably think at least a little bit before you ask questions or say things because they can, and do, get back to the PIs. For example, a student I hosted my first year as a PhD student who was interviewing for a lab that was not my own told me about how he had "6 interviews" and my school was his "4th choice." As it was pompous and completely unprompted from me, I relayed that information back to the PI because ultimately PIs want to make offers to students who actually want to come to this university.  Same rules apply for skype/in-person interviews. Try to have 2-3 questions per person you are scheduled to interview with during your visit. These help if you get stuck on questions to ask. You can often ask the same question to multiple grad students if you are, for example, having conversations with every lab member.  Bring a book or something fun, non-academic to do during down time. Depending on the agenda, you can often have hours of down time during the actual interview day, and if you are an introvert like me it can be relieving to just read a book or do something that does not involve talking to people.  It is always good to bring deodorant, gum, and mouthwash in your purse or backpack/satchel to the interview day. If you are like me and sweat bullets when you are anxious (e.g., in interviews), it can be helpful to have these handy.    
This list is by no means comprehensive, but just some thoughts that I have from my experience on both ends of the interview table. Feel free to comment and ask questions or PM if you have something specific you'd like to know about. 
 
Most importantly, YOU DESERVE THIS D*MN INTERVIEW!!!!!!!!!!!!!!!! The PI reached out to YOU, meaning that s/he thinks you'd be a good potential fit for your lab. Keep that in mind and just be yourself. 

I am turning 24 in a week. This is my first time applying and I hope I get in. I can't do any more gap years.

I took this test when I just turned a sophomore and got 810(rank 99%) and I think I could answer your question. I spent approximately 3 weeks for it. But consider I'm an international student and I had some difficulties with English terms, you could crack it in a even less time if English is your first language.
First I would suggest cracking the GRE psychology and Kaplan. These two books should be given more concentration. Memorize the summary and carefully go through all questions. Make sure you understand every question on it. 
If you have additional time, I would suggest going through a introductory book of psychology, a developmental psychology and abnormal/clinical psychology. You don't have to go into details, just go through them will help you a lot. As you know, GRE psych include only multiple choices so you can rely on your implicit memory
Good luck and take it easy!