My sheltie still grabs at my sleeves etc sometimes I do a very low pitch, firm and quick "No bite" followed by a happy excited "good boy"

Shouting is not a good idea as it raises the pitch of your voice

Thats what my trainner told me and it does make a differnce!

if you get the tone and volume correct then it works, you just have to be consitant and if you are unsure of what you are doing either go (or go back) to training school.