People might not agree with me but I suggest you buy a real tuner with a real needle.
It might be 3-4 times the price of an everyday normal electronic tuner but it's really worth it if you get into the craft of fine-tuning and maintening your guitar in shape.
I've, for years and years, only used my ears and reference sounds like sine waves.. but yeah a needle doesn't lie.
I use this:
http://www.bossus.com/gear/productdetails.php?ProductId=1003 it's probably around 100$ depending where you live.
So people pay a lot of money to get their guitar tuned in guitar shops but I'd buy a book and a tuner if I was them.
This book served me well the last 10 years, those are well spent bucks
http://www.stewmac.com/shop/Books,_...tar,_electric/Guitar_Player_Repair_Guide.html