When I took a gig doing four hours of performing at a carnival, I thought I was up the creek without a paddle. In the end, though, it went amazingly. I came prepared with everything--cups and balls, ropes, silks, sponge balls, various fruits, TT, a few decks of Bikes, and the kitchen sink.
I started trolling around the venue with a deck of cards. My plan was to do a few dozen smaller sets, then head back to my booth to do some of the "cooler" effects. I did a few variations of my walkaround card routine, with the kicker being the Ambitious Card.
Never before had I gotten the reactions from the Ambitious Card that I did the other night--I was literally getting screams... Some factors I think contributed to the effect are:
1.) "Making a mistake" and adding the line, "Your card rises to the top... cleverly disguising it as [X card]." I never did this before because I didn't really see the point, but now I realize that it adds a really nice offbeat where you can a.) get a b**** and b.) get a better reaction when their card does indeed rise to the top.
2.) Different effect. I felt like I had to take it a step above the "your card rises to the top over and over again" trick that we all start off with when we learn the Ambitious Card (I know it's not an original idea, but how many people listen to it?). I've seen other magi supplement the trick with some sort of theme (Houdini, whatever), but it doesn't fit my performing style; I'm about visual, in-your-face, and self-explanitory magic. For that reason, many of my routines can be done silently if I want to. To take the Ambitious Card, and make it even less possible, I'll vanish the card and have it appear in my back pocket (or theirs if I can pull it off).
3.) Stronger misdirection. I start with the Tilt Move. When I reveal that their card has jumped to the top, I'll look them right in the eye and say "Now, if I do this move [flick my wrist], your card should jump to the top [turn over a triple l***]. Did I hit it?" They'll look down at the card and I get my first gasp/scream/fainting. Looking them in the eyes helps cover my shoddy triple, too

I hope to incorporate some of the spec management skills that I picked up in this marathon heavily-surrounded walkaround gig into the effects I've been practicing but haven't mastered yet. Now that I'm more aware of what makes a trick great, I can practice more efficiently in order to make the improbable impossible.
Ciao,
Rob