I can't remember where I first read it, but some useful advice I read long ago is to add the opportunity for a "move" in situations where you're afraid the effect will be too perfect.
Some people would agree with that and some wouldn't. I'm one that wouldn't. The advice stems from Rick Johnsson's 'Too Perfect Theory' which is generally misstated and misunderstood anyway.
I agree with Michael Close- the whole idea of magic is that the spectator is left with NO explanation. If you intentionally create an explanation then it's not magic.
And if you're going to make it look like you did a move then why not just learn one of the versions of Invisible Deck that actually uses a move and a normal deck? There are several published.
Paul Harris has one that can be done impromptu with a borrowed deck. Michael Close has a version that isn't impromptu, but it does use a normal deck- I think the best use for Close's version is to fool the crap out of other magicians because it looks almost exactly like the gimmicked version.
Added: The Too Perfect Theory says (basically) that it's too perfect if the only possible explanation left to the spectator is the correct one. Then it's suggested (by some) that you create an incorrect explanation for the spectator to come up with.
The real question is what does that gain you? If the spectators think they know how a trick is done then what difference does it make if their explanation is right or wrong?
Generally the correct solution if the trick falls into the 'too perfect' catagory is to eliminate the correct method from the spectator's line of thinking during the presentation. If that just can't be done then don't do that trick.
In the original essay (written in 1970), Johnsson says:
It is obvious that by not pointing the spectator in another direction, we permit him to travel down a dangerous path, one which leads him to the only possible open solution and most probably the correct one. Correct or not, the result is the same
So essentially he already admits that his advice (to leave the spectator with an incorrect solution rather than the correct one) has the same result.
Few people have read the complete essay, so many don't know that it also says:
Before beginning, it is worth mentioning for the sake of completeness, that there is another approach. You eliminate all possible solutions. In the hypothetical trick of our example, you could use the spectator's deck and leave it with him when the trick is over. Now what can he think? But an easier approach is to make the trick imperfect.
I met Rick Johnsson several times- he was an excellent magician/performer and a nice guy. So I never understood why he'd advocate taking the easy way out.
While sometimes 'easier' is also 'better', that's extremely rare when approaching magic with this view.