I use my V-Amp 2s tuning function when it's there and I can be bothered to turn it on.
My main advice is get used to tuning with harmonics. It's much easier to hear the speed up and slow down of the interference waves at the higher frequencies.
Start by taking the string you're tuning low and then tune it up. This helps keep the tuning longer.
Always check back through and fine adjust if necessary. As other strings tighten or loosen the change in tension can put strings you've already tuned out. This is especially true when you're putting new strings on. On some guitars with thinner necks this can even make a difference on daily tuning.
If you're finding that the guitar doesn't keep it's tune for very long it could be that you may need to pay more attention when stringing it.
When you put new strings on put the string through the hole. Hold the string up and tight a couple of inches above the fret board with the thumb middle and ring fingers of your right hand while holding it firmly against the nut with the index finger. Wind the key keeping the tension on the string at all times. Direct the string so the first wind around the peg goes over the end poking out of the hole and then all the subsequent winds go below.
Just once more as it's important... Keep steady tension on the string at all times gradually lowering your fingers as you wind.
To start with you may occasionally find that you end up double winding at the end, particularly on the larger strings. This is not good as the overwound strings move against each other over time throwing the tuning out. You soon get an idea of exactly how much spare string to push through the hole at the start of the process for each different string.