Well with the internet it has both benefits & detriments. You should set up a search to help you quickly identify properties that as they come to the market you get to them ASAP. If what you're looking for is specific then even more important to make sure you respond timely.
One thing you might look at is how you are inquiring to them. What are you saying in your initial contact that might be turning off your chances of the landlord responding. A polite & properly worded initial contact email could be written as a word document (google document) for you to copy and paste into your email. Ask friends, family or others who you know write well and have them assist you in crafting a message to have ready.
Don't reveal too much too soon, soliciting a rental is alot like dating. Be on your best behavior and respond truthfully but mindful of how it may sound to a complete stranger. Are you revealing too much about your current situation, past troubles with rentals etc.
Another aspect is look at what email address you are using. Alot of information can be found on the internet about you just using your email address. Your facebook profile, linkedin professional information, twitter and other social networks will reveal alot of your personal life to prospective landlords. Be mindful with what you share there or restrict access to only those who you personally friend. You might consider starting a professional sounding free email account specifically for your apartment search. That way there is no personal information shared you don't have control over. What your freinds post on your social networking sites can also make an impression, along with groups you may associate with that may turn off a landlord.
With such a hot rental market in and around the Boston area, great places are going very fast and landlords are in the position to be very selective. I'd like to think that discrimination doesn't occur but sometimes individual landlords may just do that. Be prepared to search realistically. Discrimination is illegal for a multitude of reasons but you unfortunately only find out about it after you're the victim of it.
If what you're looking for is highly specific you really should consider working with a real estate professional. They can greatly assist you with searching, weeding out properties that don't match your interests and advocate/assist you in presenting your application in the most appropriate way possible. Here on Trulia there are quite a few great rental real estate professional. I've had the pleasure of knowing and working with several of them.
Hope that helps,