Well, you can get an old computer you have, hook it up to your internet and run the minecraft server off that and leave it on for the entire time. Problem is, it's got to have a fair bit of RAM and good cooling and on top of that you're going to be paying electricity bills and internet bills for running a server 24/7. You'll also need a good internet connection and a preferably unlimited plan. The alternative is to buy online hosting, although I haven't come across a service that gives free hosting.
Slightly off topic but you can use this: https://www.freeminecrafthost.com/
But you have to start the server every time you want to go on it (the server automatically shuts down after a while when no body is online)
yes I am wondering too how to make my server dedicated for free
If you want to run it from your computer, all you have to do is leave it on 24/7. But that does wear your CPU down and can be very bad for a computer. If you want true 24/7 uptime, just pick a good, cheap server host. I suggest these guys: http://maxsmcservers.com/
Solaspolas, thank you for making me no longer feel alone. I have problems like this, too, where people don't pay attention to the first post.
I'd recommend buying a brand new desktop computer (desktops are best for this purpose), installing a Linux distro, transferring all your server files, and leaving said new computer on 24/7. This way, the only way you would have to pay is in power/internet bills, and not some piece-of-crap hosting company; you would also be able to use your personal computer at the same time.
For the new computer, I'd recommend either Dell (pretty good) or Shuttle (high quality and almost silent). I would recommend Toshiba but the only desktops they make are all-in-ones, which are junk.
A full 24/7 server for free? You won't get one unless for some reason, someone is actually nice enough to give you a free server, such as a web hosting company. And you could always use an old computer or leave it up on your current one. Aside from that one website that gives you a server provided there is people on it (which I'm surprised there's even that). You're not getting a free server. It'd be nice, but then you wouldn't see a lot of servers asking for donations to actually help pay for it.
If you really want to get a good free host do it yourself. If I were you and you were serious about this, buy a 400 dollar computer on eBay that is a host of itself. One that is specifically built for running a server off of it, I got one off eBay, they aren't that expensive if you find the right one.