This may sound obvious but if you don't do it, then you decks and records will not last as long. Here's a few reason's to take care. : -

It's expensive stuff
It'll last you longer
If you decide to sell it, it'll be worth more
You won't have to do without it so often while it's off for repairs.

A good thing to do, when you first get your decks is to use the foam packaging inside the boxes of the decks and mixer as dust covers. It's just as good as buying covers and it's free. Also to keeps them free from scratches around the sides and on the bottom, put them in a box table or put a sheet on the table so it doesn't scratch the bottom of them. For the mixer wipe them as often as you can, every time you mix is a good idea, it keeps off dust and also they look good when they are clean.
For the records it's a good idea to keep them clean as often as you can, you don't have to wipe them every time you use them, but wipe the records you use the most at least once a week to keep them in good order.
For the stylus you MUST get a cleaning kit, if you wipe them with your finger or cloth it will damage them so please get a special cleaning kit.

That's all I have to say about taking care of you equipment, just use common sense and your set up should be ok for a very long time.