The popular TV show allows inventors and entrepreneurs pitch their inventions and business ideas to a lively staff of
multi-millionaire investors.
Two questions they always ask budding entrepreneurs and inventors:
1. Do you have a patent?
2. What are your sales?
The reason a patent is important is because without patent protection ANYONE can replicate the inventor's invention and the
entrepreneur's business. Shark Tank's "Mr. Wonderful" often says "I can make your product since it is not patented, and don't
have to pay you a dime for something that you don't own". 
Why would an investor put up money on an invention to manufacture it, promote it that has no patent protection? No Way!
Very unlikely, because suppose that the invention was really a big winner in sales, nothing legally stops a competitor from copying
it.  That's why it is a poor risk for an investor to take and won't take and say "I'm Out!"
What can you do?
Check the market for similar products, do a patent search, file a patent application before you invest in molds, prototypes, product
literature and color brochures.  Otherwise with a basement and garage full of your product you will become your best customer.
It is also pointed out that effective March 16, 2013, the US went to a first to file system as specified by the America Invent Act. 
What this means is that the first person to file a patent application could be awarded a patent, so speed in filing is important now
to prevent anyone else in the world from beating you to it.
Once you have patent protection and also having people buy your product is what investors need to hear. 
Start small testing the market to see what response your invention gets. Once people actually buy it with real money, you are
on the right track. If eveyone says its great but does not "put their money where their mouth is" proceed with caution and be
prepared to stop.
There are other factors that investors seek in an inventor such as passion, personality, dedication as well as what particular
problem has been solved, market size and competition.  Also whether a patent has actually issued.  
You may find good patent, sales and marketing information at HOW TO TURN YOUR IDEA INTO AN INVENTION AND PATENT IT
that may be helpful.