How can I counter these champions!!!!

It depends on who you are playing.

Check http://champion.gg/ to see which champions you play are statistically good against them (or champions you would be interested in playing) and then come back and ask for the strategy if it is not obvious to you.

: Depending on leveling path, not only will almost all of his power be in his W, but he will also be extremely likely to farm with it. Try to stand away from the minions if you can, and engage whenever he uses his Rake to farm. If you time your engages this way, you're almost certain to win a trade. Avoid using skill shots and/or ground targeted AOE effects until after he uses Cutthroat, or he may teleport behind you and cancel your ability. If you're forced to play defensively, try to lock him down if he ever auto attacks you. Being melee, his auto attacks lead to a lot of minion aggro coming his way, so if you can time your lockdown, he can lose the trade simply because you have so many minions assisting you. An upgraded red trinket is also surprisingly effective against him, as with early armor, to counter his Ultimate.

: She's extremely weak early game; her poke is flat out ignorable with even the least bit of sustain or built in resistance, and she's superbly squishy. That in mind, do not get daunted by her blades unless you as well are extremely weak early game (if this is the case, have fun, this is not a good matchup for you. As for anyone else, harass her all day as you can without overextending). Similar to Talon, avoid engaging with skill shots until you're sure she can't Shunpo, as a good Katarina will simply use that as an opportunity to engage and negate your abilities. Furthermore, save your hard CC until you are sure she either does not have her Ultimate, or for as she's using it (to cancel it).

: Surprisingly squishy. No, I'm not even kidding. Auto attack to pop his shield, wait 1 second, then wail on him. Any strong early game champion (Lane bully bruisers, for example), or any champion with a really abrupt mid game power spike (say, Level 6 LB who just bought some AP), can easily just bully or nuke him down. Obviously, avoid projectile abilities. Good times to engage on Yasuo include immediately after he tries to Q you in melee range (His Qs are treated as Auto Attacks, and draw minion aggro), after he fires his 3rd Q (during the early game, it takes Yasuo a long time to reach his mini power spike that is his tornado), and when he's isolated from minions.

: If you're a melee champion, run towards his shadows!. His shadows are only annoying because everybody, instinctively, runs away from sources of damage, which unfortunately leads to rapid increases in terms of how far Zed can teleport away if something goes wrong. Zed's W is also on a gigantic 18 second Cooldown in the early game. If he misuses it in virtually any way (a lot of Zeds like to farm with it, for example), that's a gigantic window of opportunity to abuse his now immobile and melee @$$. Beating Zed means beating his shadows. Early armor also doesn't hurt against his Level 6 power spike.

: Delay the inevitable. Zone her, harass when she farms, freeze the lane, etc etc, just do everything in your power to make sure she can't farm properly and can't afford an early Trinity Force. Past that, have fun.

EDIT: Also, speaking as an AD Assassin player, I can not emphasize how important it is not to whiff your abilities or overuse them to farm when playing against Assassins. It's one of the biggest reasons why I like to think a skilled mid lane player can win or turn around lanes with extreme consistency; learning to abuse Cooldowns can guarantee a won trade.

EDIT EDIT: Also, while counter picking is fine if you already understand how to do it and the champion you plan to counter pick with, I highly recommend against using a counter pick if you don't understand how the champion works, even if a thousand and two people tell you that it's the "perfect" counter pick. This is because most counter picks are soft or skill match ups, and you aren't going to win the skill matchup playing a champion you've never played before, if you can get what I'm trying to say.

Talon : Any Tank with a thormail with do some big damge ( I like Shen cause you can force him to attack you) Kat : Malzahar and his ult destroy her Yasuo : Champs that do not need skill shots ( Malzahar again works here, but Swain works 2 ) Zed: Kayle and ult when he ults, the slow from her Q will piss him off Irelia : The Crocodile early game rekts her, but she will outscale him, so get kills before 3force

talon - twin shado kat- knock up/stun/ knock back. save 1 skill always for her ult. yasuo - same thing like kat zed- quick silver sash irelila- atk speed/life steal atk speed reduction armour.

look up counter champs and understand why it counters. too many to list.

Your one-stop answer to countering any melee champion.

Acceptable as well if you play her well.

Morgana counters Yasuo really well I find, Build her to do burning damage with her Q and W, then shield yourself when he does the spiral wind attack, watch for his windwall though, as it can counter your Q easily. Again, as Debonare said, it's all about sharp reflexes and depends what Champion you are playing. I find it easyer to go out onto the battle field with an incentive in my mind.

Hope this helps.

I cant speak for all of them, but I know Katarina is countered by targeted, quick hitting CC like Pantheon stun or Syndra knockback. When it comes to Kat it boils down quick reflexes because she can dish out a ton of damage really quickly with her ult. Even a Vayne knockback takes too long to actually land to really counter her.* Pantheon has been my personal go-to mid laner to counter Kat.

*Note that ive never actually tried Vayne against Katarina myself, but ive seen Vaynes go up against a Kat and they just get shredded by her ult even if they knock her back.