Lawnmower won't start; now what do I do?

[Nuje]

After having a nice couple of drinks to "think", nothing has come to me.

Canadian Tire Yardworks mower with 6HP Brggs&Stratton engine. Used it a little over a week ago, and it started up fine, considering it was the first use of the year. Sputtered a bit occasionally (figured I just had some water in the fuel a bit).

But today, can't even get it to fire up - maybe I get a fire or two, but it won't catch. Never done mower maintenance before, so I don't even know where to start.
(New sparkplug...?)