I've only been to an overnight summer camp once before. This summer I am attending two and this is what I've been doing to prepare and what I've done for traveling in the past.
PACKING
I've packed shirts, pants, dresses, shoes, socks, etc., but only what I really need. I don't want to over or under pack.
You'll need one pair of plastic flip flops or slides for shared showers. Trust me.
In general, only pack what you can carry without any help.
To save space in your bags: place socks, belts, and other small items in your shoes, use the Marie Kondo folding and packing methods, if you have outfits coordinated, fold them together, and wear your biggest and heaviest items on your person (don't go crazy).
Don't forget personal hygiene products. You won't have the opportunity to buy some once at camp.
Bring a neck pillow that can clip onto your bag. You'll want for your travel if the camp is far away.
You might have free time so consider bringing something fun like books, art supplies, a small instrument, etc.
Save the environment and some money by taking an empty water bottle with you.
If you're bringing one of your most prized possessions, label it with your name! You can write on the tag or print a sticker with your name on it. You'd be surprised at how easily things can go missing.
Take a notebook and writing utensils.
Check to see if bedding, pillows, and towels will be provided. If not, bring your own that can be easily packed.
If you're a light sleeper, consider bringing earplugs, or a sleeping mask.
TRAVELING (BUS AND PLANE)
A ride in the bus or flight can be really loud or distracting. Bring personal entertainment like music, podcasts, movies, books, etc. that will last for a LONG, LONG time. If you're an introvert, I promise you that you will somehow survive.
Make sure this entertainment doesn't require WIFI or cellular data. You'll thank me later.
If you're flying to camp, try to use one carry-on and personal item/bag. It might seem difficult but this will make everything so much easier to transport and guarantee the airport won't lose it. Only you have the power to do that... just no checked luggage!
Invest in motion sickness medicine, especially if you've never flown or get carsick easily. I've been in a bus that has driven in reverse uphill. Be prepared for anything.
So I read this from a couple of different sources, but I have yet to try it. If you are flying to camp, wear a fanny pack. It is considered to be personal attire, not luggage. There are also tiny necklace or waist bags to be worn under clothing to prevent important items from being stolen.
If you're changing altitudes, your ears might hurt or pop. Don't worry, just chew some gum. This is especially noticeable when flying and will be so if you've never flown before. If you don't have gum, focus on swallowing.
Take a deep breath and be patient. You will probably be seated next to or in proximity to an extremely annoying person. You'll eventually get used to it. If someone is emotionally or physically harming you, calmly ask them to stop. If they don't stop, get a person with authority's attention. If this annoying person is a toddler or a wailing baby, I'm sorry. It might help to remember you were once that toddler kicking your seat.
MENTAL PREPARATION
I am an introverted person with social anxiety so camps can be difficult. Before going to camps, I remind myself of methods to ground myself (that actually help) if I begin to panic.
I must repeatedly tell myself that I am a very patient person who loves waiting even though this could not be farther from the truth. I focus on being grateful for the opportunity to attend camp in difficult or boring moments. Attending camp will be worth it because I will have grown as a person and learned new things afterwards.
I'm one of those strange people who enjoys to ride on planes. I think the sky looks pretty and it's the only form of transportation that I don't get motion sick in. If you do have flight related anxiety, I'm sorry. My best suggestion is distraction. You can sleep, eat, watch that new movie, read your favorite book, listen to music, or even arm-knit! You have so many option.
In the days before camp, do your best to sleep as much as possible and eat well. Generally that all will change for the week or so you have camp, so it's good to have energy to participate.
These are all things I've learned over my years of packing and traveling and going to overnight weekend retreats. I wish you the best of times at camp this summer and in any other travels! Don't be nervous, you've got this.