Showing your hand to your neighbors
In cash games there is a one player to a hand rule when it comes to making decisions. Most rooms will still allow you to show your cards to a friend of neighbor so that they know what you have and can sweat what cards come out as long as they don't offer advice on how to play during the hand. While this is allowed I wouldn't make a habit of doing this as some players may take offense to you giving information to other players at the table and not them.
In tournaments you are not allowed to show your cards to anyone until the hand goes to showdown. Showing your cards to a neighboring player will likely cause you to get a verbal warning and in some cases the floor person may declare your hand dead and you would forfeit any claim to the pot.
Talking about a hand when there is more than 2 total players in a hand
This is not allowed in cash games or in tournaments and would likely result in a warnign in cash games and a warning or dead hand in tournaments. In cash games most casinos allow you to speak freely about your hand when heads up, but many tournaments still have a no hand disclosure policy no matter if heads up in a pot or not.
Calling a clock
In most settings and circumstances any player who is dealt in to a hand is allowed to call a clock on another player after an "acceptable" amount of time has passed. After the clock is called the player in question will have one minute to make a decision. If a decision is not reached by the end of the countdown then the players hand is ruled dead. While there is no rule against calling a clock, many players take offense to having a clock called on them. I personally have never called a clock and think it is rude to do so in most cases.
Asking to see a hand at the river
This rule differs from casino to casino. In some rooms only a player who sees a hand through the river can ask to see anothers hand, while in some rooms anyone dealt in can ask to see a hand at the river. While this is allowed it is mostly frowned upon unless there is a reason to believe collusion is involved. Also beware of asking to see an opponents hand if you are being awarded the pot. If you ask and the dealer turns their hand over and your opponent actually has a better hand than you then you have to forfeit the pot to them, whereas if a third party player asks to see the hand the dealer kills it before, thus forfeiting any right to the pot if it is actually the winning hand.
There is no written rule about tipping dealers. Most poker players tip the dealer after winning a pot. The amount is discretionary and completely up to you. A generally accepted concept through the years has been $1 a hand.