Ok. Being able to play with your guitar in tune, whether by ear or with the assistance of a tuner is probably the MOST important aspect of sounding good when you play. If you are out of tune, it will not matter how well or fast you can play, it will just sound bad period. I often get asked "which tuner should I get"? So, I want to talk about a few tuners that I have experience with. There are a lot of great tuners on the market, but I will just be covering the ones that I own/use.
Allright, let's start with a heavy hitter.
BOSS T
U-2 Tuner. I love this thing. Why? Because it can sit on your pedalboard on the floor), and is right between the signal path of your guitar and amp. Why is this a good thing? Well, imagine that you are playing a live gig and you want to tune between songs. You step on the tuner pedal (which enages it) and it mutes the sound or signal going to your amp. Now you can tune silently and not make a bunch of noise on stage. With a cheaper handheld tuner you would have to unplug your 1/4 inch cable from your amp which would be a pain, and not exactly on the fly. With this one, you just step, tune, step again to turn off, and ready to play! The other thing this pedal has going for it, is that it is built by Boss, which means it is built to withstand abuse. Oh yeah, believe that Boss just came out with the
TU-3
which I am sure would be just as good if not better than the TU-2.
Moving right along we look at a tuner in the light-weight division. I have a Korg GA-20 tuner that a friend gave me some time back. Great little tuner. It has a built in mic to pic up and read the sound that it hears. If you have an electric or an acoustic with electronics you can also plug your 1/4 inch cable for improved accuracy. But again, I have good success with the mic. One final note- I believe that GA-20 has been discontinued and has been replaced with by the
GA-40 
.
Finally we have the
Intelli clip on tuner
.
1. It works great, I appreciate the fact that it picks up vibrations from the instrument not sound, so you don't need to be plugged in or make much noise to use it.
2. The bright LCD backlight is perfect for using in a dim venue.
3. It clips on to the headstock of your guitar, so it is easy to see
Boss Korg Intelli

Take care, and feel free to e-mail any questions!
-Steve
www.guitarlessonswylietexas.com