I live in Northern Vermont. I'll be happy to help, but be aware that some additive discussions start a, uh, er, discussion.
First, get to know and love the glow plug symbol on the dash. Wait until it goes out to crank the engine, even in warmer weather just to get in the habit.
Second, there are a couple of additives that make diesel fire better: a cetane booster like Opti-Lube Summer Plus and Archoil's AR6200.

http://www.dieselfuellube.com/order2.html
http://www.archoil.com/ar6000-fuel-treatments/

I use both as they work in different ways.
Third, at below 10 degrees diesel fuel can gel. I got a 6 pack of Opti-Lube Winter last winter and only used 2 of them. Below zero, you will want to use the block heater. I use an outdoor timer that comes on 3 or 4 hours prior to when I need to leave and turns off shortly after departure time. That saves on electric bills. I only plug it to the truck when the weather indicates.

 

Thanks everyone, I ended up going to Chevron vs Shell as that station is 3x the size and always busy. Their diesel is "up to 5% biodiesel".

 

Ive always used the market swing pricing to determine the "freshest". If the price is dropping then cheap diesel is generally freshest and if price is climbing then highest is generally freshest. I Definitely stay away from small stores that don't do much volume just to be safe