Inspect the spot where a snagged carpet thread connects to the rest of the carpet. If the snag is actually a partial or entire row, as is usually the case with Berber carpet, then removing the snag yourself will leave a bare spot on the carpet and it is best to contact a carpet installation and repair professional.
Lift the snagged carpet thread gently, without creating tension, to expose the base of the thread.
Snip the thread at its base just below the surface with scissors. Keeping the snagged thread shorter than surrounding threads prevents it from catching on your vacuum cleaner or shoes and snagging again.