As someone who chases fonts a dozen times a week, i use this basic method
The sample usually comes from a photo so its into photoshop, select the text, hopefully with a unique or unusual letter, fill with black then export as a jpg about 160 pixels high.
1st stop is whatfontis.com. It gives a list of 100 fonts it thinks are close. The right font is usually in the first ten but i've had matches from 30 to 60.
2nd stop is whatthefont. It used to be my first stop but i've had more success with whatfontis. They also only list fonts they actually sell. But still a very useful step
3rd stop. Search for company pdf on the web. This has helped me a lot. Probably half the time you can get a usable vector file or if you import to illustrator, it will at least tell you the names of the fonts that are missing from your system & getting the name is most of the game.
4th stop. Starting to get a bit desperate now so its time for Signs 101. One of the Gurus here usually matches it. Freds helped many times & tikiboyz is just amazing, not to mention all the other helpful citizens:U Rock:
5th stop By now i'm pretty depressed. I've tried identifont to little avail & i've tried posting to various sites & boards with little return, especially if you haven't got weeks to wait. Sometimes you have to get better artwork or use different characters & start the whole process again'
6th stop..recreate & reproduce.. you've wasted too much time on it already