I have just reached level 30 in League Of Legends and I would like to approach the ranked solo game. I read about the banning system, that allow to ban 4 champions from the game, before champion selection.
I am wondering now if there is an updated list of most frequently banned champions, so that I can check which are the probabilities that I can use my preferred champions.
There is no such list (at least no official and an inofficial list wouldn't have valid information on that).
So You just can ask some Players that have some higher ELO. Rammus is often the first character that gets banned, because of his extremly strong taunt. Vlad gets banned pretty often too, because of his high life and life leech/high damage skills. Nidalee gets banned pretty much too, though not as much as Vlad and Rammus. Then you have some characters that are more likely to get banned than others. Here's a selfmade list (not ranked/sorted at all) :
Please note that this answer is impossible to nail down, and with new champions being added at a rate of 1 every 2 weeks, on top of the meta shifting ever so slightly every few months, it's impossible to put together a comprehensive all-encompassing list. Factors like Region (EU vs. NA), ELO brackets, 5 man team compositions, FOTM picks, and personal bias all have a distinct effect on these picks.
I realize this question is old, but I feel compelled to expand upon some points here.
Note that these points are strongly tied in with the North American metagame, which revolves highly around 5v5 teamfights and lane pushing. The Euro servers have a slightly different mentality to them, and thus these may not apply there.
Being able to get to and from fights, as well as escape when low / from ganks is important. Characters with built in escapes like Shaco, Kassadin and Ahri are all examples of high mobility champions. The inability to gank these characters early-mid to mid game as well as the inability to finish them off in a teamfight without solid CC gives them a distinct presence advantage.
This is fairly broad, but characters that change how you lane can be strong options for bans at times. Ults with long range like Nocturne, Pantheon, Twisted Fate, Ziggs, or pure global ults like Gangplank, Soraka and Karthus all drastically affect how aggressive you can be in lane once those champions hit 6. This can be especially devastating for a bottom lane who is generally reliant on a strong CS .
Characters that are designed to force teamfights can often turn tides of the game by controlling when and where fights happen. Rammus, Galio, Maokai, Morgana, Amumu are all examples of strong initators (though not necessarily all ban-worthy for various reasons). These champs tend to be fairly durable as well, to survive the initial punishment they receive for forcing a fight. This doesn't necessarily have to be the case though. Sona, for example, is incredibly frail but can do an amazing job of initiating with a well placed ult.
Strong Snowball Champs
Snowball champs refer to the ability to jump farther ahead than everyone else in terms of damage/ability once they get even a little bit in front of the competition. Characters with scaling and spammable abilities, true damage, sustainability and steroids will often fall into this category. AD carries tend to fall in here, some more than others. You'll also see chain-casters (Ryze, Cassiopeia, Karthus, Vlad) and bruisers with natural damage boosts (Irelia, Lee Sin) in this category.
This site keeps a bunch of info on league including most banned, win rates per champ, and whose most popular at the time. It's updated regularly so you can check it anytime you go to play and know it's accurate. It also includes stats globally or per region as well. Some charts even sort by different Divisions to give an even more accurate depiction.
It's quite impossible to dress a list because decision's factors change according to the latest patch and your rank. I'll explain first the logic I use behing bans in rank games and then present you a tool that will gather the right informations and help to make decisions.
There are two big factors to make a decision about your ban :
Target ban (for you) : Ban the character that counters you the most (now in the meta). If you can't find the answer yourself, you can refer to the site's statistics (below) by selecting the character you want to play and then look to the zone "Champions that counter [yours]". This ban strategy should help your laning phase.
Team ban : sometimes, you will want to ban a character that is particulary strong in the actual meta even if you know you will not lane against him. By example, let's say a character X has been releashed recently and is a really strong support. Even if you are a top laner, it could be a great decision to ban it and will help your entire team. It can help your plays too at end-game stage when everyone is grouping for 5v5 fights usually.
Champion.gg is a great comprehensive tool that can help you understand which characters stand out at this moment in each role (lane), in the actual version/patch, with a bunch of statistics. For all champions, you can compare their win rates, their overall performance ranking and their ranking changes (in the latest patch). You can filter the statistics by selecting you League (Bronze, Silver, Gold, Platinum+). I would recommand you to put it to Bronze or Silver if you are a new player that just reached level 30.
Now you should be able to do the right bans in ranked games. Don't forget that the same tool and similar logic reasoning can also improve the character you will pick to play.