Go to www.dslreports.com
and use the Tweak Test, run the test, and it will ask a few simple questions. Answer them then you will see the results, and more importantly it will tell you the problems found.
Just download and run Dr.TCP to change the settings, hit save, reboot, and enjoy! If you want more proof that this helps then run a speed test on the same web page, then tweak and reboot, and run the same speed test again. Most systems that i have used this method on see a change on the incoming from less that 1000 or even less than 500 initially, to well over 1000 or more afterwards. On my particular system i noted a tested speed of 734 initially, after tweaking i get a consistent 1350-1410. Not bad considering it took only a few minutes to do!
Have fun with your DSL!