Apple Computer just announced that their earnings from the last quarter more than quadrupled mainly due to robust holiday sales of the iPod digital music player. More than 10 million iPods have been sold since it was introduced in 2001.

There are some important marketing lessons to be learned from all this. First of all, Apple has created a product for a hungry market that has the financial means to purchase it even with the relatively high price point. If you find a hot and hungry market, create a product for it and you are almost guaranteed to succeed.

Lesson #1: Find a hot and hungry market

Ever since the introduction of the MP3 file format, we have seen the popularity of converting songs from a CD so that they can be stored on the computer. Even the Napster episode showed us that there is a huge market for a device like the iPod.

Here's the summary of the first lesson - don't sell shovels to fishermen and fishing poles to gold miners. Rather, sell the shovels to gold miners and the fishing poles to fishermen. Create a product that already has an existing market.

Lesson #2: Create different versions

Now Apple just announced the introduction of the iPod Shuffle - a lower-priced version of the iPod with flash memory instead of hard drive storage.

This strategy is called versioning.

First create a product that sells. Then create another version of the product for a different market segment. In this case, Apple first came up with a more expensive product and followed it up with a cheaper product.

Lesson #3: Create the halo effect

The halo effect is essentially this: increasing sales of one popular product will generate more sales for your other existing products. In this case, the tremendous popularity of the iPod has created enough buzz that more people are buying Macs.

In the past, Macs have made inroads only to a small segment of the market. But now, we're likely to see Apple increase its market share of personal computers in the months to come.

So whatever you are selling, there are definitely some general marketing lessons to be learned from the success of the iPod. Think about it the next time you use your iPod.