I just purchased an unidentified succulent, and would like to know what it is, to best care for it.
I think it might be a variety of agave, but please advise. It is about the size of a fist, maybe 5 inches across, dark green, with black thorns on the ends of the leaves. Slightly needly edges of the leaves (not unlike an aloe).
Aha - the dead giveaway with Agave is those incredibly serious thorns on the tip of every leaf.
It's actually odd that you got one with those still on there as a lot of growers snip those off so as not to damage the workers!
I don't know which kind this is, as there are many, many different ones that are just sold as 'succulent' because they tend to be very attractive when young.
Some agave tend to outgrow their surroundings pretty quickly, and if they bloom (rarely in captivity) the flower stalk can be upwards of 30' (9 meters) tall. Keep yours rootbound and it will stay smaller longer. I rarely repot mine, and they grow only a few inches a year, or maybe 3-5 leaves. Pay special attention to the gorgeous 'water marks' on each leaf as it unfurls, where the neighboring leaf will leave its impression.
You can see more here: Agave, scroll through the entries by other visitors.
Enjoy your plant while it's still small!