Full disclosure - this is who I worked for (http://www.eriksbikeshop.com/EriksHistory.aspx)
Some things about what made ERIKS so successful:
1) bike shops make almost zero money on their bikes. The margins are razor thin. They make a majority of their profit on accessories. For example, they buy kickstands for 25 cents and sell them for $12.
2) ERIKS actually used Macs in all their locations and used a custom built POS system. They only needed one IT guy who ran 8 stores when I was there (they have around 14 stores now). He said if they were using MS, they would've had to hire a bunch more support people. It helped keep costs down.
3) At first ERIK looked for lower rent, out of the way places to set up shops. What he called, "sub-prime" locations. Rent was lower, and because of their superior marketing, they didn't need a prime location to drive traffic.
4) They trained their sales staff. This was a biggie. As a new salesperson, you went through a full sales training. You were trained in sales techniques. How to close, how to get people to buy accessories, how to approach someone, how to go through the process and asking the right questions to get to a single bike to sell. By far this is really where they separated themselves from other stores. Most places would hire bike "enthusiasts" and let them casually sell a bike if a person was interested. They had a very pro-sales approach and it showed in their numbers.
5) Keeping wages low. This is probably a contentious subject for most. But as a salesperson, I made minimum wage, with a small percentage for commission. I think it was 1 or 2% of the total sales I had. By keeping the wages low and offering in store discounts and bike manufacturing discounts (which the manufacturers offer, not ERIKS) they were able to pitch potential employees that, "There's not a lot of money in the bike industry (lie), but people who work for us have a good quality of life and good perks of being a part of the bike community." By keeping wages low, they increased their own bottom line.