Putting your newly practiced right hand tremolo to use:

It takes time for right hand tremolo technique to become smooth and well coordinated.  Eventually you should notice that it becomes easier and more second-nature.  At that stage you might be tempted to try playing one of the famous tremolo pieces such as Recuerdos del la Alhambra by Francesco Tarrega or Una Limosna por el Amor de Dios by Agustin Barrios.  Such pieces  present a significant test for any guitarist's right hand tremolo control and stamina.

As well as having to sustain a smooth or regular tremolo for a long period of up to five minutes, the player also has the challenge of coordinating this with left hand fingering.

Novice guitarists are likely to follow the sheet music from the beginning, attempting to play the tremolo while working out the left hand fingering.  A much easier and effective approach to preparing a tremolo piece is to at first forget that it is a tremolo piece!  You need to do the opposite of what you did when practicing the tremolo technique, and this time focus mainly on the left hand.

While working out the left hand fingering (which is a complex subject of its own) instead of playing the full right hand tremolo pattern ‘p.a.m.i.’, just play a single melody note together with the accompaniment notes played by the thumb (e.g. p together with m).  Any finger a, m or i will do and it should sound like a series of plain, two note chords.  This takes the pressure away from the right hand, making it easier to focus on the left hand fingering, as well as musical interpretational aspects such as dynamics, tone colour and phrasing.

Its important that you carefully choreograph your left and fingering.  At first I recommend you study the whole piece making fingering decisions from start to finish.  Once you know exactly what your left hand fingers need to do throughout the piece, you can start the process of memorization.

To begin with, play the piece at a slow or comfortable tempo that allows you to perform the left hand fingering changes smoothly and perfectly.  Don't rush.  The simplified right hand pattern will make it easier to play fast but the point is to play at the right tempo as if you were playing the full tremolo.  If your right hand becomes tired, always rest.  If the finger you've chosen for the melody note feels sore, you can always switch to another finger.  It's a good idea to give each finger (i, m or a) a turn!

The process of memorization is different for everyone but for me, with daily practice, it might take a week, possibly two, to know a tremolo piece well enough to play without the music.  The secret is to play slowly and regularly without letting mistakes creep in.  It's also important when playing slowly, to include all the changes in dynamics and tone colour that you intend to include when you eventually perform the piece.  Remember, it is music you are preparing, not a mechanical noise that any machine could produce!

Another suggestion is to break the piece up into logical sections and to practice these separately.  It's a good way to reinforce your knowledge of the music, identifying important landmarks that help the memorization process.  You can even change the order of the sections, so that you become used to starting at different points in the piece.  This technique doesn't just apply when learning tremolo pieces, but is equally useful when preparing all types of music. 

Once the left hand fingering has been practiced to the point that it becomes fluid and second nature, you are now ready to start playing the piece with the full right hand tremolo pattern p-a-m-i (or whichever one you prefer to play.)