Does July 17 sound far away? It really isn't. Right now we're in that dull stretch between the stress of registration and the excitement of Comic Con announcements, but this is in fact the optimal time to start preparing.
Save money. How obvious, right? But if you're more of a spender than a saver, this is one time you should break character and put some cash away each week, if only so you can later indulge in the orgiastic nerd spending spree to end all sprees.
Get in shape. People always get so offended when I tell them this, and then they go and they're whining and blistered and sore by Friday morning. And delaying their more energetic friends who tried to warn them of such an outcome. Comic Con is a lot of walking and standing and sitting in hallways. That's if you're an attendee; if you're working, you'll probably be on your feet a lot and carting booth stuff around. Be ready.
Join your hotel’s rewards program. Several of them (Hilton, Starwood and Wyndham, possibly others) recently went fascist when it comes to free night points, but you can still get perks like free Wifi or continental breakfast.
Make money. Instead of waiting to sell your old back issues and unwanted action figures at the Con, put some or all of them on Ebay now. Anyone, feel free to jump in and correct me - but I've heard the money and credit you get from Con vendors isn't all that spectacular, unless you have something truly rare. You're better off putting your stuff online now and holding out for the right price.
Start thinking about your costume. I'm not speaking to the cosplayers here, because you people exist in another space entirely, but the regular attendees who think it would be "fun" to wear a costume. Or just want to go native. First of all, you should know that most attendees don't wear costumes, and they can be a serious pain in the ass in terms of heat, maintenance and discomfort at a time you'll really just want to be comfortable. But if you're committed to the idea, start planning now.
Renew/get your passport if you want to go to Tijuana or Baja. Although I'd check travel warnings first.