Watch the D sus 2 Tuning online guitar lesson by TrueFire from Play Acoustic Guitar 9: Advanced Style Diversity
D sus 2 Tuning - Overview is a video guitar lesson presented by Vicki Genfan and is sourced from Essentials: Open Tunings.
(*Naming: This chord is probably more likely to be named a Dadd2. There is not actually a suspension with the addition of the 2nd chord tone. This refers more commonly to a suspended 4th which suspends the resolution of the 3rd.) This tuning has a neutral sound, because it has no 3rd in it. The chord quality, (major or minor) is undetermined. This also makes it sound a bit unresolved. Note: There's a whole step between the 4th and 3rd strings (in standard tuning there's the much larger interval of a perfect 4th), so when you play single note lines, patterns and scales that you'd play in standard tuning you're going to get some interesting surprises when going between those two strings!
Songs I've used in this tuning are Norwegian Wood, Let it Rain (both on my ‘Up Close & Personal' CD), Why Don't Love Sit Still, Outside the Box (‘Outside the Box' CD) and a song to be released on an upcoming CD, ‘I Didn't Cry for You'.
Don't forget to try using the capo on all the tunings. This one in particular has a great ringing quality capoed in the higher frets - if you let the high strings (1, 2 & 3) ring open.