Ash Wednesday is not a Holy Day of Obligation, but is a day of abstinence from meat and of fasting. The other Fridays of Lent are days of abstinence from meat. The law of abstinence binds all Catholics 14 years and older. The law of fasting binds all Catholics from their 18th birthday until their 59th birthday.
Most parishes have a Mass or service with imposition of ashes.