The Jockey
The Jockey is one of the most powerful Infected in Realism Versus. Using the Jockey's capabilities to steer people away from the pack is an extremely simple thing to do, too. Get a teammate to provide a distraction, then grab the Survivor furthest to the back and haul them backwards, keeping in mind as soon as you get out of visible range of the Survivors your job will be much simpler. A distraction should be something that puts the Survivors in a sense of overwhelming urgency. A Hunter pouncing someone does this job, especially if the pounce was a high damage pounce. A Smoker pull into a car alarm is another great example, and as always there's the reliable Boomer horde. Use them to your advantage. A lone Jockey is a dead Jockey.
The Smoker
The Smoker is another extremely powerful weapon in Realism Versus, as it also has the ability to get Survivors off their planned course and out of sight. A Smoker should also attempt to use any distraction to pull a Survivor out of sight. Also, as Smoker, use ledges, alarmed cars, and Witches to your advantage. If you are working together with a Jockey, you should realize that since you can both do higher damage and can attack from further away, you should be attacking first, providing a distraction for the Jockey to get in and get out. Try not to pull directly into the path of where the Jockey should go, and as always, never pull the Survivors forwards (unless it is over a ledge, into an alarmed car, or a Witch.)
The Hunter
The Hunter, in Realism Versus, wants to be as stealthy as possible. While you have ridiculously loud screams, you can still pounce from far away essentially muting them. With no warnings to the Survivors other than each other, they don't need to know you are in the midst of them. Not necessarily going for extremely high damage pounces, but going for mid-damage pounces (in the 10-20 range) and landing on the rear-most Survivor in a group is a great way to do damage. The reason you shouldn't always go for extremely high damage pounces is because they are both predictable, and if you miss it's very obvious that there's a Hunter in the midst of the Survivors. You are a distracting Infected. Not in the same sense a Boomer is, but you are extremely powerful and one of the most urgent Infected to kill. As such, combine your attacks with the Jockey, Smoker, and Charger for maximum effectiveness.
The Charger
The Charger, as always, is an extremely dangerous Infected. Your ability to do mass amounts of damage, send the team flying, and go off ledges with Survivors is something that is unrivaled by all the other Infected. You should attack mostly as you normally would, but bear in mind that you are a massive distraction and stealth won't really be an option. Destruction is the name of the game as a Charger, and you should keep that in mind. Attack first where possible, providing a separated, confused, and damaged Survivor team, so the other members of the Infected team have an easy time picking people off.
The Boomer
The Boomer, as always, is here to distract. Covering Survivors in bile is extremely effective in Realism Versus, for two reasons. Firstly, it's hard to see if your teammates are covered or not, and secondly when Survivors already lose all outlines, the ability to blind them further is a much needed hindrance when you're destroying the team. Use it as you always would, around corners, jumping off roofs, basically get into the middle of the Survivors and go for as many as you can.
The Spitter
The Spitter is a high damage, low mercy Infected individual. Your job doesn't change a whole lot, get Survivors out of corners (which they will be in, in this game mode.) and add extra damage to a confusion filled mess. Spitting on a pounced, smoked, or charged Survivor is a great way to do some extra damage and slow down the Survivor recovery process. Your job will not change dramatically due to the new game mode, so just use the Spitter intelligently and it will do wonders for you.
The Tank
The Tank, in Realism Versus, means the end. Very rarely will you face a team that can take down your entire team and a Tank while in Realism Versus mode. However, due to Infected error, it can be somewhat common that a team may survive past the Tank.Your team must attack with you. If you need to wait and throw rocks until your entire team is ready to spawn, do so. Do not rush in alone, unless you're completely confident that waiting a maximum of 25 seconds would put the Survivors in too good a position for you to allow. (For example, if they're currently inside and if you wait 25 seconds they will get into a flat, open parking lot.) Use your team to slow down the Survivors, and then get in there and attack the Survivors. As always, use cars and other objects to your advantage where ever possible.
You are not the lone warrior that can destroy the Survivor team. Do not think you are. You are an extremely powerful teammate, as a Tank, and you need to treat yourself like an equal member of the team for your Tank attack to be successful. More than anything, never attack a teammate in an attempt to do more damage as a Tank, and never hit a pinning Infected off a Survivor, as more often than not you send the Survivor flying as well, which can give them an escape route they wouldn't originally have.