There are a number of trusted international organizations involved in poverty and crisis relief in Pakistan, as well as a number of Pakistani organizations and companies with branches in other countries that coordinate aid in times of disaster. Contacting these organizations is the surest way to give clothing or other donations to Pakistan.
Contact Pakistan International Airlines (PIA) for information about disaster relief and donations (see the Reference section for a link). PIA responded to the 2010 flood in Pakistan by organizing a charity drive to collect donations, including clothing, for the victims. PIA delivered the aid to people affected by the disaster. Contact PIA in times of crisis to find out if it has a charity drive near your home, or if it knows of any other organizations operating nearby that are in need of donations.
Contact Oxfam International (see References), one of the largest and most trusted aid organizations in the world. It has a network of professionals and volunteers working at the local level to relieve poverty. It can give you a clearer idea of the situation in the country as well as provide you with information on how you can donate.
Contact a representative of the government of Pakistan in your region or city (see References for contact information). Websites for the government of Pakistan have pages detailing how to donate in times of disaster and what is needed. Email them for information on any charitable organizations working in Pakistan that have branches near your home where you can donate.
Contact international agencies to ask what other kinds of donations are needed in Pakistan.
Many organizations accept only money due to the difficulty and cost of shipping goods to Pakistan.