The main items are:
To be eligible you must have been involuntarily terminated-- no quitting--between 9/1/2008 and 12/31/2009.
And you need to elect COBRA (hopefully you kinda figured that one out on your own.
65% Discount on COBRA costs (paid by employers and then taken by employers as a tax reduction)
Discount lasts for nine months worth of premiums paid on or after 2/17/2009 (3/1/2009 for plans that charge premiums on a calendar basis)
Special election opportunity for individuals that would qualify, but didn't elect COBRA during the initial notice period. They get an additional enrollment period ending 60 days after the plan provides them notice.
Income limits. If your modified, adjusted, gross Federal income is over $125,000 ($250,000 for joint filiers) during the year the premium assistance is granted, the premium gets reduced-- at $145,000 ($290,000 for joint filiers) the premium is removed and must be repaid.
For more info, go here.