You want to be extremely proactive about getting your resume out to the appropriate law firms, and to make sure you are properly represented. This means working with a good recruiter, who has significant contacts and market knowledge in your specific territory. You will have to be extremely well versed and confident in discussing not only what you have been doing recently, but also the specific circumstances surrounding your departure from your last firm. How you present this information will be key to how you are perceived by future employers. I once represented a candidate who was moving to NY from out of state, and who had not worked in over 6 months. She was a litigation associate and I was working with her at a time when litigation associates were not in high demand. However, she had such a positive attitude, and she spoke with such confidence about her work experience and her abilities, that she walked out of a first interview I was able to arrange, certain that she would get the position. Within two weeks, after a second interview, she received an offer and is still with this mid-sized firm.
While you may be primarily interested larger, most prestigious law firms, it is important to keep your options open and pursue all opportunities, if you are currently unemployed. This means considering firms that may be smaller, or less well known than you would ideally like. The longer you are out of work and the greater the gap between employment, the bigger the obstacle being out of work can become with regard to your next placement. You may be concerned with how a less than stellar firm will reflect on your long term career path, but you can gain valuable hands on experience at such a firm, and it is better than remaining unemployed for an extended period of time. That is not to say that you should necessarily accept the first opportunity that comes your way, but you should remain open-minded about all opportunities and cognizant of the time frame of your unemployment.