The Major Chords I-IV-I-V-I
To play a I – IV change in the key of “A”, you might play the I or A chord as:
-5---
-4---
-2---
-2---
To switch to the IV or D chord, simply move the top three notes over one set of strings to:
-----
-5---
-4---
-2---
You can add a note to the “E” string if you want:
-5---
-5---
-4---
-2---
If you are in the key of D, and want to change to the IV chord, G, you could move the bottom three notes down two frets and over to the higher set of strings like this:
----- -3---
--5-- -2---
--4-- -0---
--2-- -----
D chord to G chord – Key of D

These physical and spatial relationships stay the same from key to key, and make a I – IV chord change fairly easy. If you are using the chop chord, the same rules apply. In the key of A move to the IV chord, D by moving the top three notes over to the lower set of strings:
--5-- -----
--4-- --5--
--7-- --4--
--9-- --7--
A chord (I) to D chord (IV)

To move from I to IV by “Chop” chords in the key of D, go (note the pinkie on the seventh fret stays planted as an anchor to make the chord switch easy):
--2-- --3--
--5-- --2--
--4-- --5--
--7-- --7—-
D chord (I) to G chord (IV)
Of course you could also use the “down two frets and over one set of strings” method as well:
----- --3--
--5-- --2--
--4-- --5--
--7-- ---—-
D chord (I) to G chord (IV)

The V to IV move in “chop” chords is very easy, just move everything down two frets:
--4-- --2--
--7-- --5--
--6-- --4--
--9-- --5—
E chord (V) to D chord (IV)– Key of A

Or using the easier form:
----- -----
--7-- --5--
--6-- --4--
--9-- --7—
E chord to D chord – Key of A

Using the other form mentioned above is also easy:
----- -----
--7-- --5--
--6-- --4--
--4-- --2—
E chord to D chord – Key of A

Move all of these chords around the keyboard to play in different keys. Notice that the physical and spatial relationships stay the same, you just play higher or lower on the fingerboard.