As soon as they release tickets for the season is the best time and those of us on the email/text update list can let you know. You can purchase single game tickets directly from ticketmaster via the Lightning website. In my humble opinion, it's probably the safest way to purchase tickets and you can see exactly where the seats are. They also list the seats that Season Ticket Members are re-selling so you can buy those if you prefer a particular seat.
There really are no bad seats in Amalie because of the way it's built. I personally avoid the corners because I like to see the Jumbotron straight on but there are no poles or supports blocking the view from anywhere. Terrace seats (where my 1/2 season seat is) are the top level, but I still have a great view from Row F.
I'm going to link you to the Amalie Seating interactive which can let you see what your view would look like from any given seat. On the Lightning website, it's under the Amalie Arena tab and is the Seating Chart. This separate from the ticket purchasing area but gives a great view of any seat!
Tampa Bay Lightning Virtual Venue™ by IOMEDIA
Edited to add: IGNORE the prices listed in the Virtual Venue as they are a few years old!