I am a postdoc at Yale, and no one including some lawyers can understand why my case got denied -- one very likely reason would be I filed service request instead of just waiting...
you (or your lawyer) will receive the denial notice and I-290B form, and you are supposed to send your I-290B and other documents in 30 days. In 290B form, you can make a choice to submit additional evidence (letters) or not. MTR is motion to reopen (or reconsider), there is a slight difference between these two MTR, MTreopen will not allow you send new document, but MTreconsider will. If you decide to file an appeal, it will automatically be treated as MTR when it arrive at the center who denied your case, and the same IO and his/her supervisor will read your appeal and decide wether they will re-exam your case. The best scenario would be they admit they made mistakes in denial and correct it and reopen you case -- it takes two weeks to at least two months depend on how complicated the issue is... if they insist their decision, then your appeal will be transfer to AAO to be a real appeal, and that means you have to wait for about 12 to 14 months and the chance for an approval is also lower than 50%.
any more questions please read PJ or XBT's articles or QQH me.
Good luck with your case and appeal (MTR)