An effective cover letter should state how you can add value.  In particular, the mission is to:

• Keep the person reading.  You want to grab the reader’s attention.  Help them to at least make it past the first sentence.
• Articulate succinctly how you can contribute immediately.  Why are you unique in a way that can benefit the firm and the person’s practice area?

Examples of typical openers (that will not likely achieve your objective):

• I am a third year student and am interested in pursuing a career in litigation.
• I would like to be considered for an associate position.
• I am writing to express my interest in…
• I am interested in working with your firm because of your firm’s focus on…

Examples of effective openers:

• My work experience as a _____________ will enable me to contribute right away to your practice.  Then, state a couple of reasons why this statement is true.
• My academic background and in particular, my focus on _________ will allow me to become an immediate contributor to your practice.  Again, support this statement.

If possible, helpful to have a sponsor

• Firm client, someone who works or worked at firm
• Then, “I was referred to you by __________ and based on her detailed description of your practice, I believe I can be helpful to you because of my relevant work experience (or academic background or whatever).”

Effective closer (ties the letter together):

• I will build upon the current success of the litigation practice by contributing my penchant for detail as demonstrated by _________.  Sell yourself but be persuasive by supporting each claim made.
• Close with the substantive items (e.g., work experience) and intangible items (e.g., attention to detail) you will contribute.  Again, support each claim made.