Encrypted data (be it truecrypt or any other software) will always look weird: text documents, etc, will have some regular or normal look. Files that contain pictures, music, compressed data, etc, will have a header that will be useful to identify it. Even programs (.exe files) will have a specific structure.
Encrypted data will look as random data that doesn't resemble any other data format. If you are looking for something inside a suspicious computer, and find a large file (or partition, or a whole volume) that looks totally random, well... it's not a regular file and you'll analyze it, and you'll bet it is encrypted.
So, how to hide a big file that looks different from a regular file?
To hide a truecrypt container (or any other program), pretending it's a regular archive: it would be a kind of steganography needs a file that's much bigger than the data being hidden. So, for practical purposes, impractical.
Another way to hide random data is to make everything else (or almost) also random. So, one would "save" random data in all empty space in the hard drive, even if that's not the content of anything else. But it would make clear that you're trying to hide something.
The only real alternative: don't let anyone get your HDD, so they can't tell if you have some suspicious file inside it.