This post comes up in some iteration every summer and while I can understand the OP's frustration the answers really remain the same and were pointed out by other posters in this thread. That said having responded every other year on this I feel obligated to this year as well.
As others have noted winning is the biggest issue. A winning season isn't going to get SU to average 45K a game but string together a few wins and people will take notice and you will start getting the casual fan who might decide SU vs NC State is a better option then fighting a massive crowd at Beak & Skiff. in early fall. Beating Clemson was a good start but you can't go and get obliterated in the last two home games against peer schools to end the season as a follow up performance.
The marketing program has also been a colossal failure. As another astute poster pointed out earlier is mindboggling how many people have zero clue about the program and really the team in general. Forget the casual fan a good chunk of the local populace doesn't even know who or when SU is playing most weekends. SU has to do a better job here. They usually pull out all the stops to get the Dome packed for one game a year (See Clemson two years ago) but that appears to be via a ticket giveaway which isn't sustainable over a 6 or 7 game schedule. Marketing department needs to get out in front for once and make the push before the season starts or at least very early in the season. Again its not rocket science, TV ads, apperances at different locations over the summer, discounts for first time season ticket holders etc. Don't be afraid to get out in the community during the season as well. If SU is on the road or on a bye week, send a few ticket people and some interns and Otto to beak and skiff or a pumpkin patch or wherever people who don't get loaded on the weekends like I do go to have fun and push single game and reduced price season tickets. Also make calling the ticket office and SU orange pack a customer friendly experience for a change instead of it feeling like your bothering these people your trying to give your money to and who usually have zero or the wrong information your calling about.
Work with the existing fanbase and with the tools the local area offers to increase attendance. SU has the advantage of basically being in the middle of the state, fan out within a 90 min radius or so and hit some events over the summer. They have the State Fair about 15 mins from campus (about 5 if Cuseregular or Bees are driving), that should be a goldmind for ticket sales. You have 10 or so day event that draws a million + people in your backyard and the season kicks off while its going on. SU should have a giant booth smack dab in the busiest area (near Chevy Court or whatever the hell its called these days) with Otto and some cheerleaders and guys like Jason Poles and others who are former players that are employed by SU pushing offers on single game and season ticket packages. Have a TV replaying the Clemson game over and over, have TexanMark demonstrating the latest tailgate equipment and have DCCuse demonstrating that it is possible to drink 3 cases of beer in a 4 hour tailgate. There is no way they wouldn't come out with major sales from doing something like that. Instead they had a booth in the least trafficked building in the place that you needed the rosetta stone to find and I don't think they have had anything the last few years. This should be a huge deal for the marketing and ticketing dept instead we get a kiosk in a hallway at Destiny, the ineptitude is staggering.
Lastly stop crapping on the fanbase that does show up. When you look at how bad things have been (save for a few season under Marrone) since P began his decline its amazing we have as big a fanbase as we do. Instead of trying to cultivate that fanbase SU spends to much time bickering with it and amongst its different departments. When you get a Sat home game at 7pm for the first time since McNabb how about leaving it at that time instead of moving it to Fri night on Labor Day weekend when have the city is either at the fair or heading for vacation. Encourage tailgating and help to cultivate the good but undersized tailgate scene that currently exists around the Dome. Don't harrass the patrons with parking attendants who think their part of the Secret Service or Gestapo. Try and find additional areas for people utilize as tailgate space and charge a reasonable price versus creating a giant parking lot across from the west lots thats now in year 3 of legal limbo with ESF and its pretty much useless on game days. Realize its not 1986 and get someone to over see the concession system who has a clue. The Alcohol options including craft beer and local wines has finally made it to the Dome over the last 5 years but the food options are the same most fans had to choose from 30+ years ago and thats coming from someone who tailgates and doesn't eat at the dome, its pitiful.
When you make a better experience and get active/aggressive in marketing the program and pushing ticket sales attendance number will increase and with winning they will increase dramatically. When you do the same thing every year and your marketing consists of a facebook post and a 45 second TV ad at 2:30 AM on god knows what channel your going to get the same low attendance numbers.