Several people mentioned remembering your customer's name. However, you should also remember your potential customer's names and/or interests. When they walk in the shop, greet them and ask them their name. Tell them yours. You're looking to create a relationship with them, and this is a subtle way of making them feel that, and feel that they - and not their money - are important to your shop. The same hold true for talking to somebody on the phone. Get their name and remember what they were inquiring about.
NEVER talk down about other shops or other brands. If you don't have what they are looking for, offer to try to get it for them, and if they don't want to go that route, recommend the best of your competitors. Really. It tells the customer that you have their best interests in mind, over your own. If their best interests and your coincide, great! If not, you want to make them happy. Even if they buy whatever at the other shop, they will trust you.
Your prices have to be competitive. I went to many LBS when looking for my first bike two months ago. I REALLY liked the one LBS. They did everything right. This was the fist shop I went to, and when I left I had decided that I was going to buy from them. I went to many other bike shops, and did research on the internet. What I found was that their prices were significantly higher than everybody else's. I called and asked if there was room to negotiate price, and they said no. When I did buy my bike, I got it for half what they were selling it for without haggling. I really want to shop at that shop - they are that good/friendly/helpful - but all of their pricess (accessories, clothing, etc.) are too high.
Check out your competition. Shop their shops. Have friends shop their shops. Find out what you like about their shops and try to integrate that into your own shop.
If somebody says they don't like something you carry, don't get defensive or try to tell them why they should like it. Offer them other suggestions. I was unhappy with the first two floor pumps I bought. When I went to other shops looking for pumps, two offered the two I had tried. When I told them I didn't like that pump, they got slightly defensive. Rather than saying, "Well, then I would suggest this pump," or "I am sorry, but these are the only pumps I carry," they said something like, "That's strange. We use these pumps in our shop and have never had a problem with them." I felt like they were saying, "I know better than you do." I won't go back to those shops.
ALWAYS treat your customers with respect, and ensure that your employees act professionally while customers are in the shop. This includes never lying to your customers. Teach your employees that if they do not know the answer to a question, it is okay (and preferred) to say, "I really don't know. Let me find out."
The freebee thing is a good idea. If somebody buys shoes and clipless pedals, maybe throw in a set of socks or two. It doesn't have to be huge. The idea is that if somebody is spending $1200 on a bike, you don't need to charge them for the water botte they bought with it. Of course, you would need to set limits. Maybe you could set up levels, where if a customer spends "100-200", you will throw in any accessory up to "5" cost. "201-400" and you throw in a $10 accessory.