Using the right tools will save you many hours of work, blisters, black finger (and toe) nails and save you from a sore back.
Some of these tools you need before you even start, some you probably already have and some you will easily be making yourself.
Before you start taking delivery of anything, yes – even before you go to IKEA the first time for your project, head to your local hardware (super)store and pick up a back brace and a dolly. IKEA makes you pack your own cart in the warehouse, and while a back brace may not be the latest fashion accessory, not wearing one may be the costliest mistake you will ever make. Save $20 somewhere else and go get one today. (And get one for your partner if you have one, as he/or she likely will be helping you)
The back brace does more to make sure you have the right posture when lifting than anything else, but that is exactly what you need.
Then head over and get your dolly. Again your back will thank you, but based on my personal experience, having the right dolly will allow you to easily perform many tasks that would otherwise require you to have somebody help you – and it will help you avoid breaking anything that you just put together. E.g. the plastic legs under the kitchen cabinets can hold hundreds of pounds of weight when under the cabinet, yet the weight of a 3-year old will snap them right off if applied sideways.
I prefer a convertible dolly, but if you already have a regular dolly, it may work for you. The convertible dolly helps you lug heavy items like a stack of shelves when converted, where a regular dolly will only hold as many as fit on the plate.
It is important that the dolly when laid down is more or less in level as you will be using it for final assembly of cabinets laying down (more about that later)
The dolly above is only $50, but prices go up from there based on construction, material and quality. It is more important you get it now than that you get one that will last for years.
You will need it when you bring your first piece of furniture home. As a rule of thumb, you should NEVER carry anything more than 15 lbs – whether it is a clay pot for your carden or shelves for your cabinet. Use your dolly and learn how to tumble your items (yes, I know you probably haven't used the word “tumble” since kindergarten, but tumbling boxes instead of lifting them means you only carry between 10 and 50% of the weight compared to lifting). If you live in a condo, and wont have space for a dolly, just think about how you later will make somebody's day at the Salvation Army store.
Finally you will need some good blankets or leftover towels to prevent your new items from getting scratched (by the ground, or by each other) and to prevent marks on your floors and walls from your new purchases. Now you are equipped to shop at IKEA.