Above all, understand the very important SAFETY information.
If there is some 'simple assembly required', take your time and follow the instructions step-by-step. Despite the apparent efforts of the designers of the mower and the manual writers to make everything as obscure as possible, it will probably go together without undo difficulty if you use the proper tools. With some, all you need to do is unfold the handle taking care not to pinch any control cables - oops - and you are ready to go to work. Happy times are here again!!
IMPORTANT: For 4 stroke engines, make sure there is oil in the engine!!! Learn how to check it and fill it to the proper level if there is none or it is low. See the section: Checking the oil.
WARNING: Running an engine without oil can ruin it in a few minutes and your warranty will not likely cover such stupidity. Since the lawn mower may be shipped without any oil, it is your responsibility to check this and then add the proper amount of the correct type of oil to the crankcase!!!
For 2 stroke engines, special oil (not the usual 10W-30/40 type motor oil, nor WD40 or 3-In-One!) must be mixed with the gasoline in the correct proportions IN THE GAS CAN - not the fuel tank of the mower! See your users manual! Forgetting to use the proper mixture can ruin a 2 stroke engine in a matter of minutes and your warranty will not likely cover such stupidity. Adding the oil to the fuel tank is not recommended because thorough mixing cannot be assured.
If you have yard equipment with both 2 stroke and 4 stroke engines, clearly label the two gas cans to indicate which equipment each is used in.