To use the common 44780 based LCDs, look for 44780 tutorials. There are a lot of them including videos. As an example, this one looks like it will help http://joshuagalloway.com/lcd.html
This is more of a list of commands than a tutorial but when I started playing with LCDs, this one Yahoo | Mail, Weather, Search, Politics, News, Finance, Sports & Videos me to write my own library. I thought it was very helpful.