The Basic Strum Pattern
The best way to describe the D chord is that it looks like a triangle on the bottom three strings. You'll be using three fingers for this chord. First, place your ring finger on the 3rd fret, 2nd string. Then your index on the 2nd fret, 3rd string. And finally your middle goes to the 2nd fret, 1st string. Arch your fingers so there are no dull notes and give the bottom four strings a strum.
The tab below shows the D chord in one measure and the basic strum pattern in another measure. Click on the second measure to loop it for practice.