After tucking the thread knot under the hem allowance, I come up through the serging stitches. I then carefully insert the needle into the fabric, picking up 2 stitches. On a fine fabric it can be one, but on most fabrics, that may cause the single stitch too much stress. It could pull, or possible break the stitch.
The right side of the fabric will look something like this. You will see the sparkle of the needle, but not too much of it. If the needle looks too visible, you have taken up too many stitches. It is a warning that your hem stitches will show.
While I am still grasping the needle in the same position, after taking a stitch in the fabric, I take another one under the hem allowance. This will become one smooth stroke as you improve your skills. I then come up again through the serging.
The final product should look like this. Of course your fabric may prevent you from totally conceiling the stitches. But if you match your thread color well and take care to make your stitches evenly spaced and uniform, you will get a professional look.