If you practice often and for more than an hour at a time, you will be able to build up decent finger strength on your own. But if you're looking to quickly build finger strength and stamina, there are an endless number of exercises you can do to speed up the process. Most finger exercises are mentally challenging as well, which adds a second degree of practice. The following examples are exercises that sound horrifying but produce great results if used actively. The purpose of these exercises is you help your mental and finger skills.

Scales

Practicing scales is the best way to gain finger strength. Simply start playing the major scale up and down at a relaxing speed. Make sure that when you’re playing notes, they are ringing through clean and there is no fret buzz. When you fret the string make sure you are pushing the string down between the frets and not directly on top of them. When you move up a string don’t lift your finger off of the fret board more than you have to. After you are comfortable play a scale. Start playing it faster and faster. Do not play any faster than you feel comfortable. Play all the scales you know, major, minor, blues, whatever you know will work.

Staircase Exercise

This is a popular John Petrucci exercise. It involves playing a staircase like pattern and inverting it and playing it again. To start on the first fret use your index finger to start and fret frets 1, 2, 3, and 4 and each finger sound be on a different string. Index finger on the E string 1st fret, Ring finger on the 2nd fret A string and so on. Pluck each string and once you get to the G invert the shape so that the index finger is on the 1st fret and the G string and pluck the strings from G down to E. After plucking the E string on the 4th fret invert the shape again and move the shape up a fret and repeat. This exercise is difficult at first but if you can get to a point where you can play this quickly and fluently you will find it a lot easier to play certain chords and even some solo lines.

Chromatic Exercises

The chromatic scale or exercise is a great way to improve your speed and accuracy. Play four notes in a row on a string and then move up to the next string and down a set of frets and go up four more notes, after that move up a string and down a fret and play up four more half steps. This will bring you to the last note of the exercise, if you want, you may continue it up through the rest of the strings if you can. Just make sure you’re playing smoothly and clean. Start out slow like all exercises and work up the speed as best as you can.