For several years now we have raised our prices a penny per square foot, along with nominal increases on stairs, with each new year. I realize that this is a very simplistic and un-sophisticated approach and Ken Snow is probably right in the middle of rolling his eyes as he reads this!
Over time I feel like this has really benefited us - we've done it even when we were afraid to do it. I think it's real easy to get stuck on not raising prices for several years in a row - there's always plenty of good reasons not to increase (times are tough, taxes are hitting my clients hard, people want a Groupon, etc. etc.)