Skateboards require only minimal maintenance, but not caring for your board can result in serious injury and could cost you a lot of money to replace gear that should've lasted a lot longer!
You've got to break in your new board! It is important to not push your new board too hard the first couple of days, but break it in doing flat ground tricks to help harden the board.
Always check and tighten the nuts before you ride and especially when you receive a new board. Even though all the hardware is self-locking and should stay tight, check it regularly anyway. Adjusting your trucks' king pin nuts will help your board turn to your liking, this is done by tightening (harder to turn, more stable) or loosening (easy to turn but unstable at high speeds) the nut till the board performs the way you like it.
Your trucks will feel sticky on a new board and sometimes they will ride to one side more then the other or one of the wheels doesn't even sit on the ground. This is normal and wont last long depending on how much you ride your skateboard. The new urethane bushings in the trucks will be 'stiff' and wont have much 'play' . The bushings will take time to break in, depending on the amount of use the trucks receive. It is important not to over tighten the bushings as this will cause them to split. If you have tightened your trucks and they still feel too loose, you will need harder bushings.
Always make sure there is no 'play' in your wheels and tighten them to the point where they are tight, but still turn freely.
The main cause of cracks or boards breaking is improper foot placement when landing tricks. Always land on the bolts!
If you want your skateboard to last, stay out of the water! It can cause your deck to delaminate (that's come apart), rust your bearings and destroy your bushings.