You need to knot. It's not enough to just bury the thread ends.

If I were making a quilt for a show, I would knot and bury the thread ends, but that's the only time I would do it. For me, I found that taking 3 to 5 *tiny* stitches shows less than sewing in place for 3 to 5 stitches (creates a little lump). The stitch length depends on the batting used, but typically it's somewhere around a .5 stitch length on my Bernina. If in a particularly worrisome mood, I will backstitch just one of those stitches, but I seriously doubt that is necessary.

I was just in a BSR class and they taught us to do a tack stitch at the beginning and the end - that way you don't get a know underneath and it doesn't show much. I liked that better than the 3 or 4 small stitches.

Nammie I would like to know more about that tack stitch.
I used to take small stiches and cut the thread, but now I am quilting other people's work, I tie off and bury.
I mainly do edge to edge quiilting and hopefully only need to do this when the bobbin runs out.
But I do get the occasional whoopsey and need to restart.
I tie off at the time by unpicking top and bottom threads for about two or more inches then starting again at that spot tying all four threads together with a square knot and bury them.
I find that works for me by using an embroidery needle with an eye big enough to take all four threads.

That is what I do too...unless I would be entering a quilt into a show for competition, then I would bury the threads with a needle.

I used to do the tiny stitches method, but I was never really happy with the results. So for the past six months or so, I've been doing the burying method where I pull up the bobbin thread, make a small knot and bury the threads into the batting using a cheater needle and I am soooo much happier with the resulting look. Nice and neat and to me, worth the few extra minutes it takes to knot and bury the threads. :)