Taking an appointment at the Boston ASC for Electronic Filing of EAD
Its all pretty straight forward really.
When you call, the representative will ask you what "ASC" (Application Support Center) you would like to go to. I chose the one at 170 Portland Street, Boston. I asked for the earliest possible appointment, I got one for the next day at 8 in the morning (on a Saturday) and an appointment number. (Keep that in your records).
They ask for your Receipt number, so keep it handy when calling over the phone. If you file electronically, you will get the receipt number when you complete the process. You dont need to wait for the physical notice of receipt to arrive in the mail; you can walk in with the EAD application pdf print out. Make a few extra copies.
Also ask for what neccessary documentation you should get along with you. I keep my documents very well organized, and I took all of them with me.
For your spouse, he/she will need to call and take an appointment on their own. You cannot take one on their behalf.
For good measure, only people who have any business with the office should visit, dont get other people with you. With the brutally cold tempeartures, the yellow security alert and since you are visiting a federal goverment office, it wont be a smart idea to do.
Regarding documents that need to be mailed:
Your application print out will tell you that you need all supporting documents on which your EAD application is based on. For me, it was the 485. So I sent them the following:
1. I765 copy+printout
2. I485 copy
3. I140 copy
4. Front and back for I-94
Write a cover letter, one page if possible, with all the relevant information. The type where the reader can see everything at one shot and can find the information he/she is looking for.
When you visit the Application Service Center for fingerprinting, they will also take digital photos. Please mention that in your covering letter. Because they take Digital photos, you do not have to send extra photographs in the mail (atleast that was true in Sep/Oct)). I look handsomer on the EAD card then I do in real life -

- Dont recommend those nasty ones at WalMart/AAA/Ritz. If you do choose to send photos, spend the moolah and get it from PicturePeople stores. (They are unbelievably good).
I also recommend you read the following URLs, besides the other ones out there:
Genearl Information on Immigration Forms
http://uscis.gov/graphics/formsfee/forms/forminfo.htm
General Tips on Assembling Applications for Mailing
http://uscis.gov/graphics/fieldoffices/scnational/index.htm#H
(If I received thousands of mails a day, I'd appreciate ones which would make my job easier to do. So everyone who ever needs to send the service centers anything should read this)
Thats the general procedure; things change over time and with the complexity of the case. I believed it could be done without a lawyer, so I just read everything on the official website and gave it a try. Check up and read as much as you can on the uscis.gov website. Dont rely only on forums and newsgroups and blogs. They are an extremenly good source if information, but use your own judgement.
Good Luck.