How does one build a search engine?

What does it take to build a good search engine? If you wanted to build a search engine where would you first start? Is there any script out there that I can start off with? Is there any free scripts anywhere that I can use for now until I can buy one or pay someone to write one for me?

Come on guys please let me know what are your thoughts on this?

There are free scripts out there.....But that's exactly what doesn't make a succesful search engine. If you want a successful search engine, you have to conceive a great idea, something that has never been done....Google did it with the worthless PR, Yahoo did it by being the first recognizable SE....You have to come up with something unique....It doesn't have to be useful, but it does need to be something that you can say that only your search engine has.

Yeah, like jumpenjuhosaphat said, you need to be different. There are plenty of search engines out there, what makes you think I'd like to (or others) use your search engine over the bigger alternatives such as Google? Impress me! Show me something interesting! Then I'll use your search engine!

Then again, I didn't ask what this search engine is for Do you mean a search engine for the entire web? or are you looking to make some sort of internal or specific search engine?