What are lame files?
Lame files are first and foremost files without an ed2k-hash. AniDB uses the ed2k-hash to identify a file, and thus, files without ed2k-hash are a real hassle.
There can be a few other reason for lame files, but the ed2k-hash is the most important one.
Other, less serious reasons, for lame files are when other parts of the fileentry aren't specified.
CRC not verified
When things like the CRC hasn't been verified, this is considered a lame file - note that even files where the CRC is invalid aren't referred to as lame files, since the official CRC has been looked up and noted to not match. Files with invalid CRC should only be added if you have reason to believe the corrupt file is widespread. If you're unsure about the CRC, leave it as it is, or try to find out if it is correct on sites like Envirosphere or Baka-Updates.
If the file doesn't have a group added, this is considered a lame file - even though the fact remains that some files aren't worth putting groupnames on, like self-ripped and such (though those should generally not be in the DB at all, instead add them to your MyList as Generic files).
RAWs are also a hot topic of discussion when it comes to this, but generally, if you know who actually encoded the file, put their name as group. A lot of the raw groups don't do this, please help us by telling us which raw groups to credit.
Files that doesn't have a quality-rating, are considered lame, but this is not very serious - the quality-rating is very subjective in any case, and is likely to change as technology develops - 10 years ago, VHS rips were the standard and considered quite good, while nowadays, you usually frown at their quality. And H264 is replacing XviD and DivX, just as RM was replaced by superior AVIs a few years ago.
Another point to be made is that subtitle files shouldn't have a quality rating added, as they contain no video.
In the case of ed2k-hash, if you have the file in question, you could use AOM to hash the file if you're on windows, or WebAOM on any OS, then you will have to add the ed2k-hash to the file by editing it or filing a creq.
If you don't know the group, you should check first the file - there might be information about the group in the video or subtitle streams. If that fails, you should try to check the place you got it from, if it is an actual person, ask them whose file it is.
In the case of no quality - watch the file, and see what you think. If it is only a subs file, then don't bother.