You can do a simple search: milk cookies will seach for images with milk and cookies in the description, but not necessarily next to each other.
You can use common boolean operands: milk and cookies does the same search as above.
The "or" operator can also be used: milk and cookies or chocolate will also include descriptions containing chocolate.
Since "and" binds before "or", you can use parentheses to group terms and change their order: milk and (cookies or chocolate) will find descriptions with milk, and either cookies or chocolate.
Finally, you can ask for descriptions to be excluded: cheetah and not Ch'marr will find descriptions with cheetahs, but not a certain cheetah.
The search index is tuned for English words, and will try to 'normalise' some of them. Eg: vixens will find "vixens", "vixen" and "vixening". You can search for exact words or phrases by enclosing it in quotes: "vixen's party"
If you get no results, try removing common words from your search. (This is a bug, and will be fixed).
If the server is busy, your search will be queued. Refreshing will not do any good.
More recent images are weighted slightly more favourably.
Remember, VCL doesn't allow fan-art without permission. There's no point searching for commercial character names, here.
Search via Google Images
Google retrieval and indexing patterns will mean recent uploads will not show.
Long descriptions will cause search to match the image following the image it was supposed to return. So, make sure you check the whole index page.
The search will turn 'SafeSearch' off; you'll get no images otherwise. You may get adult material. Be warned.