For accounting, I think there are some big firms in the last ten years that would disagree that nothing interesting happens. 
In all cases, I'd start with the person who answers the phone and answers the email inquiries. What questions do they get all the time? What information do they send out by email? How much of that can you put on the web, to both draw traffic and to ease some of the phone calls and emails you get with basic questions?
Someone can order concrete, but how much hand-holding do they need to choose which type of concrete to order? How do they know how to judge how much to order? If it's for a pathway to my front door where two people live, do I need a different mix than if it was a sidewalk at an elementary school that has 800 kids? What about permeable concrete that lets rain go through?
What size forklift do I need? What considerations do I need to take into account when ordering one? Are there some that are too high for common garages? Do I need any training to use one? What if I need one for just an hour to unload a unit of plywood, can I get the delivery person to wait while I unload so they can take the forklift back? What happens if the plywood delivery is late and you end up serving lunch to the forklift delivery person? (this paragraph is all based on personal experience!)
Those are more for content than link building, I realize. For links, perhaps a local real estate agent has a column about DIY concrete driveways and could recommend your client as a reputable company? Could they sponsor a little league team and be sure that the team has a link back? If they're a member of the BBB or trade organizations, be sure to get links.