No matter what you are planning to do.. "Tourism, I am here to see the country (see friends, relatives etc)" I almost made that mistake before but remembered to shut up just in time.
Lying, even when the lie is "conventional" can cause problems as well; many immigration agents are very good at sniffing out little inconsistencies.
I once spent about three hours arguing with immigration officials in "the back room" after a friend decided that "tourist" was a better answer than the real reason (going to a wedding, staying with my family)—but that didn't quite match up with other details ("where are you staying?" "how long are you here?" ...). [Note this was also prior to 9/11, and they probably err on the side of "grill" more often these days.]
The guy that did most of the grilling in that case (and who seemed pretty sharp) ended with this advice: "next time just tell the truth... it's a lot easier for everybody."
Hard to say really, didn't work in this case. Another friend of mine has been told before by passport control to just say "tourist" when she gave an answer that wasn't "I'm here on holiday" whereas customs then grilled her minutes later on why she said "tourist" when she was there for a wedding.
The thing is, though, once you're in the back room, they can fairly quickly determine if you were lying, and if you did lie, that itself will be held against you. Unless you have a very good explanation for why you lied—and do a lot of groveling—just the lie can be enough to deny entrance (even if the truth is innocuous).
Explaining a non-lie can be annoying as well, but not having lied is a much better position to start from.
During the second interview in the back room it was fully explained why my friend was there. The woman in charge then told her "It doesn't really matter what you tell me now anyway, I'm going to base it off what you said the first time around." Even after I got to explain the thing again on the phone to the woman later she said if that's the case she made a mistake but there was nothing she could do about it at that point as she "just stamped the paperwork so no reversing it now."
I once spent about three hours arguing with immigration officials in "the back room" after a friend decided that "tourist" was a better answer than the real reason (going to a wedding, staying with my family)—but that didn't quite match up with other details ("where are you staying?" "how long are you here?" ...). [Note this was also prior to 9/11, and they probably err on the side of "grill" more often these days.]
The guy that did most of the grilling in that case (and who seemed pretty sharp) ended with this advice: "next time just tell the truth... it's a lot easier for everybody."
I think that's pretty much true.