There are three ways of getting Leaf tickets:
1) Be waiting at ticketmaster.ca when regular season tickets are made available
2) Know someone who has tickets
3) Buy from a scalper business or person
The easiest but most costliest option is number three. You're usually looking at paying 1.5 to 2 times the face value for the tickets. One place I used this past season is ticketcentre.com. Call them up, pay by credit card and they'll courier the tickets wherever you like. Expensive but you'll be able to get tickets when you want them. There's always eBay as well.
If you're going to try option one make sure you find out when tickets are made available. They're gone in mere minutes especially anything greater than singles.