The best and frequently easiest way to play any given chord is to isolate just the notes you need and find a place to play them on the fretboard.

For things like B minor and C-sharp minor it is as simple as finding the 3 notes that comprise each of those chords.

B minor - 1st (B), minor 3rd (D), 5th (F-sharp)

E |--2----------------------|
B |--3--3-------------------|
G |--4--4--4----------------|
D |-----4--4--4-------------|
A |--------5--5-------------|
E |-----------7-------------|

C-sharp minor - 1st (C-sharp), minor 3rd (E), 5th (G-sharp)

E |--4--------------------|
B |--5--5-----------------|
G |--6--6--6--------------|
D |-----6--6--6-----------|
A |--------7--7-----------|
E |-----------9-----------|

For more see my Chord Inversions tutorial:
http://www.guitartricks.com/tutorial.php?input=148