Applying for a green card is usually a two-step process consisting of the filing of a petition (by your relative, spouse or employer) with the INS, and the application, which can be made at the US embassy or consulate in your home country. You can file with the INS if you are in the USA on a non-immigrant visa at the time. As applications differ depending on the category, you should ask the advice of the consulate.

The following are the categories of those who are eligible for green cards:

• Immediate Relatives: Including spouses of US citizens; unmarried people under the age of 21 who have at least one US citizen parent; parents of US citizens if the son or daughter is over 21.

• Preference Categories: These are people with family members who are US citizens (under these categories certain family members will be given precedence over others: children of US citizens have priority over brothers and sisters, for example). The second preference category is those with job skills that are wanted by US employers and are in short supply in the USA.

• Ethnic Diversity - Diversity Lottery: Also known as the Green Card Lottery: 55,000 green cards are given to those countries who in the past have sent the fewest immigrants to the USA. At the time of writing Great Britain is not included in this quota, although Northern Ireland and the Republic of Ireland are included. You must register by a certain date each year, and if the registration is accepted you file an application, with documents such as birth and marriage certificates, at a consulate. You must provide proof of a high school education or its equivalent, or two years' work experience within the last five years in a job which requires at least two years' training or experience. One hundred thousand people from six geographic regions are given the right to enter the Lottery, of which half will win a green card. Some seven million apply every year.

• Investors: As a result of the Immigration Act 1990, 10,000 green cards are now available to those who invest between $500,000 and $1 million in new US businesses that will hire at least ten full-time workers.

• Special Immigrants: Over the years various laws have been passed covering certain `special categories' of immigrant. These include religious workers, foreign medical graduates, former employees in the Panama Canal Zone, foreign workers who were formerly long-time employees of the US government, and several others. Check with the US consulate for details.

• Refugees and Those Seeking Political Asylum: To qualify you must be fleeing political or religious persecution in your own country. Economic refugees (those escaping poverty) do not qualify.

• Temporary Protected Status: This is not a green card category: Temporary Protected Status is given to those fleeing persecution who need a temporary safe haven. It will not lead to a green card.

• Amnesty: The Immigration Control and Reform Act (ICRA) 1986 gave amnesty to aliens who had been living illegally in the USA since January 1 1982, by giving them green cards. Special Agricultural Workers (SAWs) and Replenishment Agricultural Workers (RAWs). Under ICRA 1986 those who had worked in agriculture for 90 days between May 1 1985 and May 1 1986 were given green cards. The second category (RAWs) are those who worked for 20 days within a calendar year and registered before December 31 1989, who were entered into a lottery. The system will be revived whenever there is a shortage of agricultural workers.