Arpeggios are part of every guitarist's formative experience and daily life. As the most ubiquitous technique in the repertoire, they deserve the attention they get. The most common resource used is the "120" patterns offered us by Giuliani, an exhaustive collection of patterns oft-reprinted, including in the popular technique book Pumping Nylon by the inimitable Scott Tennant.
The way I teach arpeggio practice differs some from what others do, though, so I will offer it up here for general consideration.
I am happy to use some of these patterns as a launch pad for this type of work, though only the ones which feature sequential patters (not the ones which include double-stops or larger chords). Pick a pattern, say, p-i-m-a. Use a two-chord sequence as suggested by Giuliani (any open-string pair of chords will do--don't stick solely to C-G7). Regarding RH preparation, I recommend that, as each note is played, the next is immediately prepared. I don't advocate "block preparation" for ascending arpeggios.
Play each arpeggio pattern in the following 18 ways, each version going fully through the two chords, four beats-per-chord, at least once.
1) Play firmly, evenly and exactly with the metronome.
2) Emphasize p, free stroke (play i-m-a quietly)
3) Emphasize p, rest stroke (play i-m-a quietly)
4) Emphasize i, free stroke (play p-m-a quietly)
5) Emphasize i, rest stroke (simile)
6) Emphasize m, free stroke
7) Emphasize m, rest stroke
8) Emphasize a, free stroke
9) Emphasize a, rest stroke
In each of these versions, grossly exaggerate the difference between the loud and the soft volumes. Don't sacrifice tone, though, in the loud notes. I realize it is unusual to insert a rest stroke into an arpeggio but this technique is enormously useful when an accent is called for or when trying to "bring out" and inner voice in a complex texture. It may require a soft tip joint so as to avoid pushing the hand out of position.
10) Starting in a neutral position, and gradually over the course of one or two chord cycles, move the right hand to the 12th fret for ultra-dolce tone, then to the bridge for ultra-ponticello tone and back. Repeat.
11-14) Select four discreet right hand positions between the 12th fret and the bridge. In each location, gradually morph the timbre from warm to brilliant and back by slowly changing the nail angle. This will incorporate both the subtle angle of the fingers and the angle of the wrist.
15) Slightly arch the wrist and turn it some to the right. At this angle you should be able to produce a warm, full tone with p while at the same time playing a bright naily sound with the fingers.
16) Slightly turn the wrist to the left. From this position, look for a bright, tinny tone from p while producing a thick dolce from the fingers.
17) Starting at a neutral volume (mp-mf), gradually decrescendo all the way to a near fade-out, then gradually crescendo to your loudest possible volume, then back to neutral. Repeat.
18) With other elements remaining neutral, double-time the arpeggio. If not possible, then simply pick a faster pace a try it a few times. If you can play twice the original tempo, then after doing so, double-time AGAIN (this will be really fast, and is likely possible only in unidirectional and other simple arpeggios).
That'll do it!
I recommend students pick two different patterns and stick with them for a week or two, then roll in two new ones. Cycle dozens of patterns over the months in this way. I recommend students change chords between patterns (i.e., for two arpeggio patterns in a day, use a separate chord sequence for each) to keep it both aurally fresh and prevent left hand cramping. (Try Dm-A7, Am-E7, G-D7, Em-B7, etc).
I use other arpeggio activities also, naturally, but this routine is my central launch for right-hand training. As it includes many elements that will prove useful later when interpreting music, it can have a deep impact on technical/musical development.