#1 - A Detailed Quote
First things first, an estimate is not the same thing as a detailed quote. As a legally binding contract, you need that detailed quote to know exactly what materials and services, among other things, that you're paying for. Basically, this quote will include every single cost of your renovation, such as the prices for preparation, materials, installation, and finishing. Never hire a team that doesn't offer a detailed quote.
#2 - Properly Acclimated Surfacing
As an experienced renovation team, they're well aware of the acclimatization process. Essentially, this critical process involves measuring moisture and temperature on-site, to gauge how long it will take for surfacing materials to regain their original form. Should these materials expand or contract before or during an install, they will most likely end up malformed or damaged.
#3 - Clear, Calculated Measurements with Layout
In no way should materials be purchased and layout planned sight unseen. Every room is different, different dimensions, different obstacles, and as such cannot be planned out without prior measurement. What's more, it's essential to discuss plank directions, as this will greatly affect renovations.
#4 - Subfloor Preparation
Subfloor preparation should also be included in the detailed quote. That means everything from the cost of materials like underlayment, to the time it takes to haul out old plywood. As well, even though you'll have no clue what state your subfloor is in, the cost should also include any potential, unforeseen repairs.
#5 - Proper Fastener Usage
Improper fastening is a big No-No, and can result in the reduced lifespan of your surfacing. When you get hardwood floor installed by professionals, they'll let you know what type of nails will be used and where they will be placed. If they don't bring it up, ask them about it before they start any work. Typically, pros use pneumatic nailers, assuring that each nail attaches to each board properly, thus limiting movement or loosening over time.