Hopefully this thread can answer everyone's questions about purchasing or acquiring tickets. Please not, we do not allow members to sell tickets to one another, so please do not make a thread asking to buy or sell tickets from/to someone on here.
Single Game Tickets: Before the season starts, a limited number of single game tickets are on sale through ticketmaster.com and through the Denver Broncos website.
This is the official Ticket Info page for the Denver Broncos.
Single game tickets usually go on sale in the second half of July, and an announcement on the exact date they go on sale is usually made in late spring or early summer. When they go on sale, this link (as of spring 2013) will lead you to the page where you can purchase tickets.
If tickets are sold out through ticketmaster:
The NFL Ticket Exchange is the official resale market to purchase your tickets. Note that these prices will likely be higher than face value.
90% of the seats in the stadium are accounted for by season ticket holders. The current wait list to join the season ticket holders is 7-10 years.
Feel free to post questions in this thread.