It is imperative to always be in tune whether you are just practicing at home or in a jam room and especially important if you are in a studio session or on stage! There are certain guidelines you can follow to ensure you are always playing an instrument tuned to perfection.
1) Truss Rod: Take a look at your fretboard. Look at it from the angle in which your eye should look downward from your headstock towards your bridge and not the other way around. If your fretboard is not straight and seems a bit warped it could be due to seasonal changes and would need an adjustment. You must visit a guitar technician in this case so that they can take a look at it and make the required adjustment that should ideally make that view from your headstock to the bridge as straight as possible.
2) Bridge intonation: If your truss rod seems fine then the next step is your intonation. Intonation is basically nothing but ensuring the accuracy of the pitch of your note across all places on the fretboard. Check the 12th fret of your instrument to ensure that you are getting an accurate pitch response that is relative to your open string pitch. If this is slightly flat or sharp you would need to adjust the intonation screws accordingly. If you are uncertain on how to operate this you should visit a guitar technician.
3) Re-stringing: When you change your strings make sure you’re winding enough string around your tuning pegs and also ensure there is no overlapping of string while restringing. Any sign of a string overlap or not being wound neatly could result in an improper pitch/intonation and could even cause your string to break during performance.
4) String Pull: Once you are done with re-stringing then tune your guitar to your desired pitch. After tuning it to pitch, lay the guitar down on your lap and start pulling each string upwards toward your face gently. If there are any loose ends in your winding that are not severe, they could be fixed in this process.
5) Bending your strings: Once you are done with the above exercise check your tuning. If your tuning has been compromised it means that the strings were not wound as tightly as they should have been. Now tune up your guitar once more and start to bend away those strings one at time, especially the higher strings! You will notice at first that your pitch would flatten as you bend to the higher notes. Keep repeating this bending process for at least 10 minutes so that the strings sit in and get used to the tension of the instrument.
Once you have successfully gone through this entire process you would then realize that no matter how much you bend those strings they would continue to stay in tune!