From what I've seen, I've seen people assign numbers and use a website to pick one of the numbers at random from the list.

That's simple enough.

When making the raffle, make sure you include 3 base parts to the flavour text (the description of the raffle)

1) What the raffle is about - Why you're holding the raffle (could be because you're celebrating something like hitting a pageview/watcher milestone or even just because it's your first ever raffle...), etc.

2) What the prize will be - Tell people what the prize will be if they win. This could be anything from a sketch to a full-colour piece to a piece with one or more of your character/s... to a slot in a massive tentacle orgy, etc. Also tell people how many winners there will be. And this part is IMPORTANT... Whether you are the artist for the prize or not, then show some examples of what they will win (and if you're NOT the artist, then show pics from the artist's gallery that will match the quality of the prize). I can not tell you how important that is. It might not seem like much, but more people will join if they can see what sort of prize they'll be getting.

3) The rules - There are a few main rules you'll want to put in for people to enter.

A. Make sure people are watching you and/or the artist... and word it so people know NOT to unwatch you/the artist after the raffle is over.

B. Tell them to promote the raffle in a journal and link it back in their comment on the raffle. You can specify if you want it to be a separate journal or if you don't mind it being in a grouped journal...

C. Partially optional, you can ask people to post their ref/s for their character there and then... though some people won't bother with this one and only get the ref from the winner.

D. OPTIONAL - Tell people they have to say a specific word/phrase in their comment. This is usually to make sure people actually read the rules. If you put this, do NOT back down on it. It's aggravating when there are those of us who specifically follow all the rules enter a raffle and then have the raffle won by someone who didn't even bother to read the rules, let alone actually follow them...

So yea. Those are the main 3 points I'd make when doing a raffle. You can either promote it via a journal or in a picture submission (which works even better if you're doing a YCH piece as the prize)

I hope all that helps :3

Thank you very much for all information, you really helped me very much and I will use this in my future raffle ^^

You're most welcome.

I look forward to entering said raffle :D

Oh! And thanks to Lehran for pointing that out...

When people enter, you CAN assign them numbers if you so wish (though it's not necessary).

To find the winner, the easiest way to choose is using Random.org to pick. It works even better if you number people as they enter the raffle because Random.org has a simple random selector where you can just tell it to pick between numbers 1 and XXX (the latter being the last number in the raffle after you close it)