How can i make sure that no one can use my company name?

I recently researched this info. And as I understand it you cannot patent, copy right or copy guard a name. To prevent someone from duplicating a name you would need to get a trademark which I believe someone posted the government site to visit.(http://www.uspto.gov/ )
You have to begin by researching the name to be certain no one else has already registered it. You can do this yourself or there are company's who perform a search for you for a fee.
There are many online companies who do this however, to be wise you would need to research the company before you selected one to be certain of their credentials.
If your a patient and fairly intelligent person you could probably do it yourself but I imagine you would need to research little deeper than I done to be competent.The government site includes instructions and the search can be done online as well as downloading all the necessary paperwork.
If you can afford to hire a trusted attorney. That would probably be the easiest, safest solution for you.
Once you have determined no one else has already used the name you file an application at the US trademark Office of registration. There is an application fee.
Can't remember for sure but I believe the fee for what I was wanting was around $150.The figure$350 or $400 sticks in my head to get and file all the required forms.
At any rate, probably around $500.00 total. Just to give you a ball park figure.(Excluding attorney fees or paying someone else to research for you ,if applicable)
This is for the US only. If you want it world wide then you would need to follow the requirements set by each individual country.
I also read where in some cases you don't necessarily need to have a patent, copy right or trademark to prove ownership of an idea or name.
My father was an inventor. He patented his ideas he put into manufacture. But some of his inventions that he didn't believe there was a market for at the time, He simply drew a diagram and wrote down the specifics of his idea then mailed it to himself and never opened the letter. The sealed postmarked envelope was theoretically suppose to show he had the idea first.
I don't know if that is actually a fact but I think at the very least it leaves room to question if there should be a law suit filed so I would not rely on that soley.
But if you added having a notary sign and date the material, photos with time/date stamp, and possibly photos with a current newspaper headline and date, etc. It might come more near holding up to scrutiny.
However, this may entail you having to file a suit to prove it in court. I wouldn't recommend it.
Research it on the internet. Perhaps you can find some refuteable site to help you. Some legal sites offer a free legal consultation.
I actually used one of them a few years ago for some friends and found it very informative.I think it was freelegaladvice.com(not sure)
Hope this helps. God's peace be to you.
Faith