Okay first things first. Look in to how the con does artist tables, every con does them differently. For the two cons I go to Portcon you buy a table for all 3 days, costs $60 for a full table (6ft) and $30 for a half table (3ft.) You submit an application to apply for a table, so you might not get one. Furfright how ever does artist tables like a raffle, it's free but you probably wont get a table all 3 days. So get to know how they do things, and when they open for applications. Don't get discouraged if you don't get a table.
Second off budget yourself, keep track of your spending. You need to make back what you spent, other wise you just wasted time and money. Keep in mind though that includes badge, artist table, and if you get a hotel room.
If you do get a table some thing that are a must have. BUSINESS CARDS! FOR THE LOVE OF CRAP! They should have your name (sudo name if you wish) some way to contact you (email works great) and if you wish a web addy to where your work can be seen. This way even if people can't afford to buy something, they can still contact you after the con. Best way to get business cards for cheap is do it yourself. Got a printer? Get some nice 110# card stock, and go to town. Takes a little more work, but you don't pay $30 for 100 cards that could end up looking crappy. Displays are good ways to show off more of your product, especially if your space is limited. In your case with tails and ears a simple rack or box of some sort to elevate and pin your work to. Being at eye level attracts people. Shiny things to do, so if you have some spare cash and it's after a holiday get some candy on sale. Give it out to people who buy something. Everyone likes free candy, and they could tell their friends.
Now I know you said you're using your mates laptop to show your work, make sure you bring an extension cord, and tell the artist staff you need an outlet. Other wise, when that battery dies your out of luck. Have a price list for commissions some where people can see it. As well as tags that say how much each item is, a simple back and white printer is your best friend.
If your going to suit around I can't stress enough HAVE A HANDLER! They keep you safe, and not just from walking around. Kids at conventions don't always get that you built that costume, it costs you money, and YOUR INSIDE! But if you suit and have an artist table, find someone you can trust to watch your table. Never leave your table un attended, other wise things might go missing.
I know there's more but my mind is going blank at the moment.