Open Dm tuning
The open Dm tuning (DADFAD) gives a lot of interesting prospects and easy ways to create lovely music on the guitar. If you strum all open strings, you will get a D minor chord.
When you retune your guitar, it is important that you turn the tuning pegs in a direction that decrease the string tension and not the opposite.
To get the open Dm tuning on your guitar you tune it like this: D A D F A D.
Including an octave perspective, the tuning is written D2-A2-D3-F3-A3-D4, meaning that the lowest string is a D note on the second octave, the second lowest string is a A note on the second octave and so on. Standard tuning reference: E2-A2-D3-G3-B3-E4.
In addition to the presented D minor chord, two other choices in open position are Dm6 (00020) and Dm11 (032203). Notice that Dm6 is atonal (the B note aren't part of the D minor scale).
The Em11 chord is more correctly written as Em11/A (notice that the 5th is omitted). It can also be written as A7sus4.
The Fmaj7 chord is more correctly written as Fmaj7/D (which also can function as a Dm9 chord). Notice that it can also be played as 000002 with the 5th is omitted (which is similar to the Dmadd2).
The Gm chord is more correctly written as Gm/Bb. Notice the similarity with the Em7b5.
The A7 chord is played with an omitted 3rd and can also be written A7(no3). If the D-string is played open (X002020) it would be an A7sus4.
The C chord is more correctly written as C/D. A regular C major without an alternative bass note can be created with the fingerings X3223X.
The C9 shape becomes as C7 if it's modified to X3221X.
Movable one-finger (or slide) shapes
Dm, Gm and Am represent the diatonic chords in the D minor scale. But obviously you can play others as well with one finger. For example, Em as 222222 and Bm as 999999.
Other possibilities for one-finger chords in Open D minor tuning:
These chord shapes are movable. Gm7 will therefore result in an Am7 if the whole shape is moved two frets up.
There are often many options to play certain chords (especially minor chords) with barre shapes since five of the strings are tuned to the two notes. For, example, Gm7 can also be played as 555585 or 588555.
Other possibilities for barre chords in Open D minor tuning:
An option is to place a capo on the second fret, which will result in an Open Em tuning.