I am an investor who is looking at using the PEG ratio to evaluate stock. How do you estimate earnings growth?

You are not estimating earnings growth, financial analysts do this. Also, make sure you know what time scale the company reporting this number is using. Common periods are 1, 3, and 5 year PEG. Lower P/E ratios and higher EPS growth equal lower PEG, which means the stock is undervalued (good if the stock catches up after you buy it). However, you must remember that these are all projections! If a company misses their earnings, then the PEG means nothing. GE missed their earnings recently by only 7cents, but that equals $700mil. This should not be the only thing you look at, because it is so speculative. Look at past earnings reports. Did they meet/beat consensus? Are they actively expanding the company? Any recent upgrades? S&P ranking? Do some tech analysis. Is the stock oversold? Take it all in before investing. Otherwise you could lose based on someone else's predictions.

???? Analysts and the company make an estimated guess as to how much a company will grow in the next years. Problem is that those are just guesses and are usually overly optimistic. I was looking at PEG as well a year ago but I no longer rely on it. Many of those low PEG companies run out of cash and fail.

Shoot, I was looking at BRLC who makes TVs and they had ridiculous low PEG of .34 when they were $4. Problem is they burn through cash and are at $1. Based on PEG, they seem like a great bet. I look at ability to generate cash flows.