So I have an invention idea but do not really know how to go about

This is a question everyone starts with. I think one question you'll need to answer is what path do you want to take with the product idea? Do you want to make it and sell it? Do you want to license it? What's your goal with it. From there, then you can map out your plan. There is always risk involved, but there are definitely warning signs. Stay away from anyone or company who makes wild promises or the "sure thing". If it's too good to be true then it usually is. There are companies out there like Edision Nation, Quirky and others who help people in your scenario.

You can't trust anyone with intellectual property. If your concept is truly novel, anyone you show it to needs to sign a NDA (non-disclosure agreement).

From there, depending on the product, you want to document and date the invention by applying for patent pending status with the USPTO (United States Patent and Trademark Office).

You'll need an intellectual property or patent attorney to do this correctly.

If you're bootstrapping and low on cash, you're going to need to find an angel investor who can fund this.

The easiest way to get VC funding is to put together a professional prospectus and presentation and then present the product (after execution of NDAs) to companies with similar or complementary product lines.

Once you have legitimate interest from a company, you can easily get VC funding if necessary.

Alternatively, you can always go the crowdfunding route with something like Kickstarter.

Take a look at the Mom Inventor's site for great ideas, books to read, etc.

You are right to be suspicious. This industry is filled with vultures and consultants who, for a fee, are willing to tell you whatever you want to hear. If their advice turns out to be wrong or otherwise worthless, they don't really care -- they already got your money. I've seen many companies ruined this way.

Instead, you should find an experienced person in the field and ask him or her to be a part of your company. Offer them a healthy equity slice in exchange for their contacts and know how. This way, he or she has skin in the game and incentive to have you grow as quickly as possible. By making them a part of the team and given a large equity slice, they are unlikely to steal the idea, as they would only be stealing from themselves.
The really good ones are hard to find. They don't need you. They certainly do not come out to tech meet ups, or seminars or what ever watering hole entrepreneurs like to hang out at. You have to do your research, find them, and convince them that they can make a lot of money by joining your company. IF they like you and the idea, they will do so. If not, ask them why not, and make whatever adjustments they desire.

Ideas have no value unless executed. If I say I have an idea of creating a robot that can reproduce like humans, the idea sounds great however it has no value unless it is executed. I may fail, however, if I become successful then my idea can change the world. It's worth that risk.

I can help you in converting your idea in a product. I have been doing this since long. Let's setup a call.