Suspended chords, whether the sus4 or sus2, are rarely played for very long. They are very unresolved sounding, and more often than not, their role in the piece of music is that of a 'passing chord'. A passing chord, as the name implies, is one that you 'pass through' on your way form one chord in a progression to another. There are other chords that use the 2 or 4. You may see in tab or chord charts symbols like 'Cadd2' or 'Gadd4'. This means that rather than replacing the 3 with a 4, the 3 is retained and a 4 is added to the triad notes. You'll find that add2 chords are much more common than add4, which have a very dissonant sound. You will also see chords written '7thsus4' ... this simply means that it's a 7th chord (dominant) with a 4 instead of a 3. I haven't done diagrams for them, but you should be able by now to figure them out for yourself. Building chords is really not very mysterious once you know the 5 basic shapes and that Holy Grail of formulas, the Major Scale: TTsTTTs.
Suspended chords are those that replace the 3 of the chord with either a 2 or a 4 ... in other words, one of the two scale notes that is either side of the 3. Remember that the 3 is the note in a chord that determines whether it's major or minor, so by replacing it, that major/minor quality disappears. I guess that the term 'suspended' comes from the fact that the major/minor quality (which is the main identifier of any chord) is temporarily suspended. The sound of these chords also has a 'suspension' quality about them ... an unfinished, something-needs-to-happen sound.
The most common of the two types of suspended chords is the suspended fourth, or sus4, where the 3 is replaced by a 4. If you remember your TTsTTTs formula for the major scale, you'll see that the 4 is one semitone up in pitch from the 3, so sus4 chords are easy to figure out if you know the major shapes ... you just need to 'sharp' the 3, or 3s if there are more than one. The term 'to sharp a note' means that you raise it in pitch by one semitone, or one fret on a guitar. When you sharp a 3, you get a 4.
The green dots show you where to put your finger tips. The red crosses mean 'Don't pluck/play this string'. The blue numbers indicate the best left hand fingers to use.
1 = index; 2 = middle; 3 = ring; 4 = pinkie.
The C and G forms have two 3's that need to be raised, so they're a little clumsier than the A, E and D. If you look at the images below, you'll see how the 3s in the original major shapes — the all-important CAGED shapes — have been raised to become 4s. Chord building really is as simple as that, it's all numbers and once you know which numbers are which, it's simply a matter of adding them to or subtracting them from those five main chord shapes.
The A and E forms of this suspended 4th chord are the easiest to turn into barre chords, but you can move fragments of any of them up the fretboard to become new sus4 chords. For example, if you moved just the notes on the three top (thinnest strings) of the Dsus4 chord up 2 frets, you'd be playing another Esus4 chord. You would not be able to play the three bass strings of course, you'd have to avoid strumming or plucking them, but that's OK.