Generally, you are thinking about your job search correctly. Having not gotten any results from your efforts so far, you should be asking yourself (and others) what you should be doing differently to meet with more success in your job search. Even so, your question assumes that the hurdle you are encountering has to do with how you are transmitting your interest to the firms. I don't think that's a safe assumption.
Let's talk first about timing. You are looking for something that will start in the Fall of 2010. One of the by-products of the recession has been that law firms are seriously reducing their expectations for how many new associates they are prepared to take on. Though I don't encourage people to spend too much time pouring over all of the bad news coming out of law firms, it is important to know what is going on in the industry. For the last several months, many law firms have been announcing that they are deferring start dates, both for incoming class of 2009 and class of 2010 lawyers. Some law firms have cancelled their summer programs, some of seriously reduced their summer classes. What does this mean for you? It means that there is a great deal of uncertainty about future hiring needs. By applying now for a position that will start in a year, you are essentially asking a law firm the question ''will you need someone with my skill set this time next year?'' In today's economy, the answer is almost certainly ''who knows?''
Here's the good news. Some firms are un-deferring entry level lawyers as they see that there is some increase in work to go around. We are seeing the market incrementally improve. Still, the recovery is not so vibrant that firms are willing to gamble on their needs so far in advance. Law firms are conservatively evaluating whether to bring on associates. They are making decisions to do so only when they see an acute need for new lawyers.
I think that your candidacy is simply too speculative for many firms at this point. I suspect you will be far more successful with inquiries when you are closer to the date that you actually are ready to make a move to a new position. I would suggest that you re-evaluate your efforts in the Spring. We anticipate that the hiring landscape will be much brighter.
Regardless of the timing of your search, you are correct that how you send in your materials to a prospective firm are important. I do think that many hiring partners and professionals like electronic submissions, so long as the cover letter and resume are perfect. I think that there is a tendency to be too casual and too sloppy via e-mail. If you can avoid this trap, you should be ok. Having said that, do everything you can to find out what your target law firm's preference is in terms of their preference, and conform your presentation accordingly.