All waitlists are not created equal.

Take the cases of both Dartmouth and Tufts. In short, Tufts seems not very promising, and Dartmouth seems to offer a slight glimmer of hope. 

TUFTS
Tufts does not offer much information publicly. Last year, they did not accept anyone from their wait list. Not even one student. They did not report any information about wait list admits in the prior two years. Tufts does make mention of "typically anywhere from zero to twenty-five" students admitted off the wait list in a blog post (see link below).

Unfortunately, Tufts does not provide its statistics to the College Board, either. However, take a look at the image below, "TUFTS-2015", from the Tufts 2014-2015 Common Data Set paperwork (http://provost.tufts.edu/institutionalresearch/files/CDS_2014-2015.pdf). This is a fact sheet required by the Federal government.

Yes, that is ZERO admits off the wait list from last year's admissions cycle. 

For 2013-2014, Tufts chose not to answer. See "TUFTS-2014" below. And they also did not report for 2012-2013. See "TUFTS-2013" below.

Are you seeing the numbers? Or more correctly, the complete lack of them?

If you prefer more clarity than just a few zeros, here is Tufts' page about their wait list, with their advice.

DARTMOUTH
There is more information available on Dartmouth's wait list. The statistics have varied over the past 10+ years from as few as ZERO admits off the wait list to a high of over 100 just last year (2015 fall entry).

Dartmouth College Wait List Statistics (from the College Board)
Fall 2015 entry
Waitlisted: 1852 
Accepted place on waitlist: 963 
Offered a place: 129

Fall 2014 entry 
Wait-listed: 1855 
Accepted place on wait list: 1133 
Offered a place: 0

For more information, and trends over time, see DARTMOUTH -10 YEAR WAIT LIST HISTORY below for a chart showing wait list acceptances from 2003-2013 at Dartmouth, based on numbers released by Dartmouth under mandated Federal guidelines. The article in which this data is found is here: Dartblog: "Waitlist Use Up Again"

There's even more information on Dartmouth's website. An important page to read is this: Waiting List Information | Admissions - which is Dartmouth's procedure for the wait list. 
 
The LinkedIn article below outlines how wait lists are used, and how to approach them.  It's lengthy, but filled with great advice from Parke Muth.

TUFTS - 2015

TUFTS - 2014

TUFTS - 2013

DARTMOUTH - 10 YEAR WAIT LIST HISTORY

Stand out from the crowd of college applicants. Create your story around a theme that is unique to you. 
  
Rome wasn't built in a day.
Developing your story takes time. Start by getting involved: take part in extracurricular activities at school, delve into academic interests, and explore careers via internships. The payoff: a better idea of your academic strengths and a narrower set of activities that matter to you. Your themes will emerge where these intersect.

Add commitment, initiative and leadership.
Pick one theme and build your story around it by pursuing your interests with sustained commitment. Will you teach yourself a programming language like Python and write an app for your school? How about participating in scientific research at a local university, blogging about it, and presenting your work to faculty and students? Can you start a special project to support one of your volunteer commitments?

It's all about you.
Be authentic. Create a challenge that fits your unique strengths and interests. Uncover your story.