Embroidery on knits can be tricky, but the real secret is in the hooping.
To get great results on knits, you must stabilize this stretchy fabric.
You probably know that the text book rule for fabrics that stretch is to use a cutaway stabilizer.
This should be followed, except in rare instances. If it makes you more comfortable, you can use a fusible cutaway.
This prevents stretching during the hooping and the embroidery processes.
Properly hooped, fusibles and spray adhesives are not needed to prevent shifting on most standard knits types.

1. Cut your stabilizer large enough to completely cover the outer hoop ring.Pre-cut stabilizers sized specifically for your
hoop size are available. Check www.expertstabilizers.com for dealers of Deborah Jones' Expert Stabilizers. 
2. Mark your placement using tape or Target Stickers made by Designs in Machine Embroidery. The long reference line helps assure straightness in the hoop.

3. Place the inner ring inside the outer ring at the top of the hoop.
4. Pull very slightly downward to create a light tension on the fabric.
5. Insert the bottom of the inner ring.

Test the tension on the fabric by doing the Lift Test. Try to lift the fabric off the surface of the hooped stabilizer. It should not be easy to separate.

Now, do the Snowplow Test. Run your finger lightly across the surface of the hooped fabric. Don't press down too hard. The fabric should not "snowplow" in front of your finger.
Turn the hooped knit over and make sure that it is all the way in the hoop.
If it is, place the hoop in the machine and your knit embroidery should come out great!

See more tips and watch videos at www.myembroiderymentor.com