I found free motion pretty challenging at first. The easiest way to machine quilt that I have found is to use a walking foot and just make gentle curves from one end of the quilt to another. Unlike stitch-in-the-ditch, you don't have to watch closely to make sure you stay in the ditch (or near it). Unlike free motion, all of the stitches are made evenly by the machine. All you have to do is guide the quilt through from one end to the other. If you make these wavy lines in both directions you end up with a crosshatch design. If you are nervous about machine quilting, I think this is the best way to start.
I personally always starch the quilt backing heavily because then I can be confident that I am not going to have multiple puckers and tucks in the backing when I turn the quilt over. My method is very easy. I mix a 1:1 solution of Sta-Flo liquid laundry starch with water, put the fabric on the kitchen island and "paint" it with the mixture using a house painting brush, throw the starch-saturated fabric in the dryer, then iron with steam.
Spray-starching the top is a good idea for the same reason; it helps prevent stretching of the fabric and the formation of tucks and puckers as you quilt. This is especially recommended if you decide to make your wavy lines running from corner to corner, as quilting on the bias increases those possibilities.
I highly recommend spray basting your quilt sandwich to save a lot of time. For machine quilting, it is often recommended to safety-pin baste the quilt sandwich; however, I ruined an expensive Bernina walking foot that got caught up in a safety pin I didn't see to remove in time. Spray basting is just plain easier as well as much faster than pin basting.
If you really want to free motion quilt, you need to make up several small quilt sandwiches to practice on first. Muslin or any scrap fabric and batting you have on hand. Make these practice quilts about 18" square or so. You will learn a lot about free motion quilting by trying it out this way way first. Most people have a steep learning curve with fmq. That's why I recommend doing real quilts with the walking foot and curvy line approach.