If you read “Win the Green Card Lottery the COMPLETE Do-It-Yourself Guide” and follow the instructions there is no reason why you cannot easily register for the lottery yourself at the official government website providing you have access to the computer and a decent camera. In fact, registering is now so easy you don't really need any help at all if your situation is straightforward and you have no questions about the U.S. immigration system. Registering yourself will save you the cost of the lottery service fee. The average cost is about $50-60 USD per person for one year and $70-80 USD per married couple for one year. However, there are some good reasons to use a paid lottery service.
For one, applicants can use an ethical lottery service any time of year and not scramble with changing dates and requirements. Unfortunately, the U.S. State Department changes the registration dates for the green card lottery each year. Even worse, they don’t bother announcing the actual dates (almost always a narrow 30-day window beginning in early October) until mid-September. Others like the peace of mind of getting their application and photo reviewed for errors.
But in most cases the convenience of letting someone else notify you if you win is sufficient reason to use a service, especially if they have contacts with good U.S.-based immigration attorneys. Better lottery services notify winners both by telephone and email. Many can also offer legal help directly to lottery winners. Legal assistance is not a requirement, but can be extremely useful or mandatory depending on your particular circumstances. And a good immigration attorney can provide assistance with other types of visas.
It is surprisingly easy to lose your official confirmation number after you enter since so much time elapses since your entry and your Electronic Status Check. Unfortunately, if you lose your number you cannot check your entry and you cannot win -- just like any other lottery. However, a lottery service will not lose your number. In the 2011 (“DV-2013”) fiasco, many discarded their confirmation numbers the first week of May after the U.S. State Department mistakenly notified 22,000 applicants that they won. Unfortunately, it is not possible to check winning status without the confirmation number.
I can’t tell you how many times I’ve received emails from entrants saying they lost their entry confirmation with the number. Any reputable service should provide you with your official confirmation number in a timely manner after they enter your application with the U.S. Government in October. This will also allow you to check for yourself online to see if you won.
Some services even pay for your travel (airfare) to the USA if you win. Since travel costs can be prohibitively expensive for overseas applicants, many are willing to pay extra for this option. With multi-year entries for an entire family and other options, the total fees can run into the hundreds or low thousands of dollars. However, be advised that travel costs represent only the start of the expenses if you win. For example, the U.S. government charges winners a Diversity Visa Surcharge fee of $800 per person.
Lottery services should spend extra time cleaning up poor paper photographs that would normally be rejected by the government. (NOTE: beginning two years ago, the government created an English-only web app that allows entrants to fix many digital photographs so they will be accepted by the entry process.) Some services accept applications received as late as one week before the closing date of the lottery but usually charge an additional fee for processing last minute applications.
If you do use a service provider, make sure you use an ethical one. Although Google has helped clean up the industry by refusing to permit some types of lottery service advertising, they have also inadvertently blocked ads from some good, ethical services for failing to follow their new strict guidelines. But Google let other advertisers slip through that provide extremely shoddy service and/or overcharge entrants with exorbitant fees and useless options. Bing has no restrictions on green card lottery service advertising, as least as far as we can tell.
MyGreencard.com helps lottery entrants select an ethical service by reviewing and rating services each year. This list of qualified services and rating criteria is maintained at: http://www.mygreencard.com/review.php.