On the car insurance topic, it is worth noting that it's illegal in most (all?) states to operate a vehicle without insurance. AT ALL. Like, you can't even drive it home from the dealership if you don't have insurance. This doesn't usually pose a problem for most American buyers, because they typically already have a policy on another vehicle (their parents', or a previous car), which typically includes automatic coverage on new vehicles for, say, 14-30 days. Since you won't have a pre-existing policy, it will be a bit trickier for you. If you're buying from a dealership, they may try to offer you insurance through some agency partnership that they have. That's probably not the best price you could get. Instead, it is probably worth shopping around in advance with a few different insurance companies that you think you might want to do business with -- you can get quotes online by providing some basic information about the make/model of the car, and driver history -- and then call them up to ask what the procedure would be in your state for starting a policy on a new car at the time of purchase.
Depending on the state, the dealership may provide you a temporary license plate, or they may facilitate you paying the taxes/fees and receiving an actual metal plate from them. If you just get a temporary plate, then you usually have 30 days to visit your state's DMV to complete the registration, pay any remaining taxes or fees, and receive the final plate.
As dcmustachio said, when purchasing a car, your proof of ownership is the title. If buying with a loan, the title is in the lender's name until you have paid off the loan. Otherwise, the title is in your name. If buying from a dealership, you should have no issues with this. If buying from a private party, you will want to make sure they sign over the title to you -- if their name is not on the title, do not proceed! There is usually a space for signatures at the bottom or on the back of the document. Oh, and verify that the VIN (vehicle identification number) on the title matches the vehicle.
I second the recommendation to use tax prep software. But you also should not feel intimidated to just download and review the official forms and instructions directly from the IRS web site. The language is generally easy to understand, and I find that it helps to refer to the "official" rules even if I'm using third-party software to file my taxes. The deadline to file a tax return is typically April 15 (i.e., 2014 taxes must be filed by April 15, 2015). However, you cannot wait until then to pay your taxes owed. The U.S. requires ongoing payment throughout the year. For most people, this is handled automatically by their employer via withholding from their paycheck. If you are self-employed or ER but still have taxable income, you must make quarterly estimated tax payments throughout the year.
The laws governing landlord/tenant agreements vary quite a bit from state to state. Once you know for sure where you'll be settling, search online for terms like "tenant's rights" and your city or state. Ask for a receipt for any deposit or advance rent. It is wise to do a walk-through inspection of the property with the landlord before you move in, and note any pre-existing damage in writing (and take photographs) so they don't try to blame you for it when you move out. Find out if any utilities are included in the rent, or if you'll need to pay for them separately. Read the lease thoroughly to understand what the rules are for payment of rent, when and how the rent can be increased, rules for eviction, what happens at the end of the lease, and whether you are allowed to terminate the lease early. In some states, you become a "tenant at will" (aka "month-to-month") once the lease expires or if you do not sign a longer-term lease. Insist that all agreements be put in writing.