Are you going to have a table or just be walking around the con? I'm assuming the latter since this is such short notice?
Get some business cards or some other small item with your contact info to trade with people you talk to. Personally I rarely actively try to hand mine out but I do trade them with people I meet so when I get home I have a small collection of cards to remind me who I met. Most conventions also have a freebie table where people leave cards and flyers and things for anyone to come by and pick up.
A lot of people do flyers but if you've ever been to a con where someone was actively pushing full size flyers you've probably noticed discarded ones everywhere. People don't keep them. If you want to do something like a flyer keep it smaller, like a quarter sheet. People will be much more likely to keep them if they fit in a pocket or a notebook.
My personal favorite thing to trade is mini comics, probably not a lot of people will have them at a sci fi con but at indie comic cons they're very popular. One sheet minis cost about the same to print as full size flyers and unlike flyers people generally enjoy being given one.
In general though just try to talk to people and be friendly. Try and approach people as if you're meeting a potential new friend as opposed to someone who can advance your career. If you're just trying to promote yourself people will notice and instead of remembering you as the nice and cool person with a cool comic you'll be the remembered as the annoying person who only cares about promoting their comic.
TL;DR Be the nicest coolest person you can be and if you're going to give out a physical thing make it something people will enjoy being given.