Before you do anything else, get all your fabrics prepped for cutting. If you are making clothing, you'll want to wash your fabrics first. How ever you plan to wash and dry your finished garment, do that to the fabric (warm wash, tumble dry; cold wash, hang dry, etc.). The bolt end at the fabric store will tell you what the fiber content is and give you the recommended care instructions.
If you are not making clothing (items like curtains, bags, toys, quilts, etc.), it is generally better not to wash the fabric first, because washing removes the sizing and crispness that will make those items last longer. If your non-clothing items will be washed frequently (i.e. slipcovers), wash the fabric first to make sure any shrinkage will occur before you spend all the time making it.
Pressing the fabric before you cut is only neccessary if it is terribly wrinkled or there are creases that resist flattening. If you press, do so as a single layer of unfolded fabric.
