1. A permanent address 
Google your roofer before you hire them. If there’s a local physical address and a building, odds are they’re reputable. If they show up in an old truck shoddily dressed with out-of-town plates, beware! They may be unfamiliar with Maryland code. There’s also a chance that they’re storm chasers from out of town, who’ll split before they finish the job.
2. A track record
This is a tough business that swiftly weeds out the disreputable operators. Fact: Most roofing companies don’t stay in business longer than 5 years. The guys who’ve been around longer have reputations they’ve built and are intent on protecting them.
3. Insurance
Make sure they carry liability insurance and workman’s compensation for every worker who comes onto the site. If a worker causes damage to your home or gets injured while on the job, you could be held liable.
4. They’ll leave your garden as they found it.
Contractors hauling ladders and heavy equipment can crush delicate plants and lawns. You don’t need the expense of paying for a new garden along with a new roof. Make sure they commit to leaving your garden intact or pledge to replace anything they damage.
5. They bring their own dumpster, and they don’t dump it on your driveway. 
An old roof generates a ton of garbage. Somebody’s got to haul it away, and it shouldn’t be you. Make sure that they hire someone to do the job. Better still, make sure they have their own dumpster. That way, they can’t blame a sub-contractor for failure to remove the refuse. You don’t want their dumpster on your driveway either. The weight alone could crack the asphalt.
6. They won’t leave your garden and walkways littered with nails and metal scraps. 
Stray nails and metal scraps are inevitable on any roofing project, but they don’t belong around your home. Just one stray nail or metal shaving can puncture your car’s tires or injure your kids.
7. They don’t destroy your gutters in the process of building your roof. 
Make sure their ladders have stabilizers that keep the weight off of their extension ladders. Each ladder weighs hundreds of pounds and can tear your gutters off. The stabilizers will ensure that they’re intact at the end of the project.
8. There’ll be a supervisor on site throughout the project to address your concerns. 
Roofing terminology can get pretty technical; you need someone accessible at all times to answer your questions or address your concerns.