The United States is a very large country. It is larger than Europe and 2.5 times larger than India. From the east coast to the west coast, there are many cities and attractions. You should try to pick one or two areas and visit them. Otherwise, it would be very hectic to try to cover everything.
In the US, restuarant waiters are paid very little per hour. They have to depend upon tips to make their living; therefore, tips should not be considered optional. The amount you give to them should based on the service the resturant provided; some restaurants calculate the percentages on your receipt to make it easy for you.
There are many public places where smoking is prohibited. You shouldn't attempt to smoke anywhere you like as there are usually designated smoking areas where you are allowed to smoke.
Americans are highly punctual and they usually arrive on time, unless some major reason such as accident or unexpected circumstances arise. Therefore, be on time. If you have to be somewhere at 10 AM or if the show or the attraction is supposed to start at 10 AM, it will start at that time.
You should always observe the traffic signs and laws. You simply can’t cross the street anywhere you like. You also can’t park anywhere you like. Don't park in parking spots reserved for a disabled person if you are not disabled and don't have a valid placard from the Department of Motor Vehicles.
Unlike almost everywhere else in the world, the US still uses the old system where the temperature is in Fahrenheit instead of Celsius. No meter or liter either. Instead, you use miles and gallons. It might take some time to get used to it.
There are many national parks for the nature lovers. There are many big cities with skyscrapers. There is snow, mountains, desert, and beaches. There is something for everyone and for every kind of interest. Therefore, prioritize what you would like to see most.