I travelled by myself last summer when I left home at the end of June to pop half way round the world and visit my best friend who had been studying a semester abroad in Auckland, NZ. I felt confident that I could navigate the airport and connecting flights, but i still wrote a comprehensive list of what time each flight was, what time it was boarding, which terminal it left from, and which gate (if i could find the information online!)
Although i was later than i would have liked buying my flights, I purchased them about three weeks before the fly date, they weren't too expensive. Make sure you're in constant contact with your American employer, and ask if the start/arrival date is flexible. There is a massive price difference between certain days, times, and flight durations, and thankfully my employer was flexible, so i was allowed to arrive two days later than i said i would when originally accepting the job. This saved me £200, which was useful for the first few weeks of living expenses.
There have been studies which prove that Wednesday is the cheapest day to fly, due to most holidays wanting to start/finish on the weekend, with Friday and Sunday being the most expensive. Flying early morning (yes, that means being at the airport at the crack of dawn) is usually cheaper, but it also means you can sleep once your on your flight. Take a look at slightly different duration flights also if you want to save. For me, it was cheaper to get a slightly later flight, but with a half 40 minutes less time in between my two connecting flights. Shop around, and use the STA travel price match, because if you find a cheap deal online with a non-budget airline, they will match it for you.
Make sure you have all your documents, i bought a handy document wallet for only £2.99, and it meant i could keep my passport, visa forms, money, and important bits of information all in one place inside my carry on luggage. In the week running up to your flight, make a list which you can keep adding to as you remember things you need to bring, because I can guarantee if you leave packing till last minute like I did, you'll remember that there are things you wanted to pack, but you wont remember what they are!
Things to make sure you've brought with you;
Hand luggage bag containing anything to make your flight more enjoyable, such as magazines, ipod, inflatable neck cushion, earplugs or eye mask, contact lens solution and glasses if you wear them.
This can also double as your day bag when you go and visit other cities or have day trips away from where you work. Choosing a 'uncool' bag with a strap for each shoulder will cause you a lot less hassle in the long run that trying to bring a tote bag or fancy designer handbag.
Passport. Obvious, but I'm sure there are people who forget this every year and end up missing their flight. Make sure there is a page in there with your VISA on, which has your picture on.
DS-2019 or as it says on the top of the form 'Certificate of Eligibility' which you would have got outside the embassy appointment. If someone asks for your reference number from this, its the 11 digit number in the top right corner.
SEVIS I-901 Confirmation is the piece of paper stapled on the reverse of the DS-2019, and just proves that you have paid for the privilege of working in america over the summer. Again, this will have been given to you at the embassy appointment.
Reservation details of any bookings you may have made at the other end, such as shuttles from the airport, or confirmation references of the hostel you are planning on staying at if you aren't going straight to your destination. I landed in JFK airport in New York, and took a Supershuttle to my hostel, because i could prepay for it when i was still in the UK and that gave me peace of mind. I just had to provide the reservation number to the lady on the transport help desk when I landed. My employer also emailed me with details of how to get from JFK to Martha's vineyard where i would be working for the summer, and which coaches i needed to be on and what time to change etc, so its a good idea to print these off so you have something to help you if you get lost, and need to ask for directions. My hostel for the one night was also pre booked, but not paid for. I had to ensure i had enough money to get some food if i wanted in the airport, pay the $60 for the hostel for one night, plus some extra 'just-in-case' money.
CIEE Card is the little blue, white, yellow and red debit card sized plastic thing that tells you the number you need to ring when you enter america in order to let CIEE know you've arrived. This should be up with your documents because its important not to lose it, and to be able to access it soon, not lose it at the bottom of your luggage.
Proof Of Funds/Money, which I were told would be needed at the immigration point of the airport to show I could sustain my life whilst in america for the first few weeks before a pay check. I had cash with me, but you could also take a pre paid card with a up to date receipt showing the amount on it, or a recent online banking statement. However, i was not asked for proof when entering.
There may be the option to self check in before your flight, and print off your own boarding cards. With aerlingus it was upto 36hours ahead of departure. This could save you loads of time at the airport, meaning you just have to drop your bag in at the check in point, and then go through security. its always worth asking to check if your bag is going to go straight through to your final destination if you have multiple stops, you don't want to end up in America with your luggage still going round the Dublin luggage carousel...
Finally, its also worth putting a little post it note somewhere in your hand luggage and checked in luggage with your home address, address of the place in america where you'll be staying (or working) if you know, a phone number and your passport number. This means if anything gets misplaced there's contact info readily available.