Search online for the basics of how to patent your idea. Do not use any online company to help you with patenting & marketing your idea -they are generally rip-offs.
You need to spend some money to do this right. After some basic research, look for a local patent attorney to work with, try to use someone you can meet FTF, not online.
The first thing you have to do is to decide if it's worth it. If you have a new design, can you afford to protect it in courts if a company steals it? The most common occurrence is an overseas company steals your designs and ships to the USA. Can you afford to do product searches and have attorneys to serve "cease and desist" orders and follow-up in court? can you afford to sue everyone that steals your idea?
*understand that if you only have a design idea and not really a new method of manufacture or operation, it will be really hard to protect. All someone needs to do is to change the design by around 5-10% to get past your patent.
The second thing to do is to make a patent search -maybe that idea/design has already been patented. You want to make sure that you are not infringing on someone else's patent.
Ultimately, you have to decide if you can make money with your idea, if you can't, then it isn't worth patenting. This is what most knifemakers do, they just rely on brand recognition to differentiate their design v. copycats.
