My house rules are different in every game I've run. Giving you a specific set is probably meaningless. But here's how I approach house rules, as described in my "Rules for DMs" document. [Yes, there's some redundancy here. I wrote a couple of these this morning, after reading this thread. Editing will come later.]

Spoiler: Jay R on House Rules and DM Rulings
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11. The DM can change, annul, or overrule any rule in the rulebook. This is not a toy or free privilege to change the game at whim. It’s a heavy responsibility to make the game go right, and to be fair to the players, even when the rules aren’t right for a specific moment.
a. Printed rules should be the standard. Rules changes should be the exception.
b. Never ignore the rules. When you change or make exceptions to the rules you should be most focused on the written rule, its intent, and its effects.
c. Applying the published rules is like eating food. That should always happen. Changing the rules is like taking medicine; it's only a good idea if something is wrong, you know how it’s wrong, and you know how to fix it.
d. Never change a rule unless you know why it was written.

12. The more completely you know the rules, the better you can be at disregarding them when necessary.
a. "When necessary" means it should be rare, forced by an unusual situation, and non-intrusive. [And some people believe it should not happen even then.]

13. Do not confuse house rules with rulings that overrule the book. House rules are the conditions that make your world distinct. Overruling the rulebook is preventing a rule from messing up the game. They require different approaches.
a. House rules are conditions of the world. They should be planned in advance. You can do it just to explore a new idea, or to create a unique situation.
b. Overruling the rulebook is fixing an immediate problem. You should do it when the rules give an unfair or otherwise bad answer.

14. House rules are ways to create a new, exciting, unique world, with new concepts for the PCs to explore. They are not merely tools to stop standard tactics from working.
a. When you introduce a house rule, ask yourself “Why?” Will this make the game better for the players?
b. They should almost always be introduced before the game starts. It’s fine for your goblins to have deadly fangs; it’s not fine for your goblins to suddenly develop deadly fangs halfway through the game, after the PCs have faced them and learned about them.
c. Tell the players any house rule that is a generally well-known fact in the world. If necromancy is more powerful when the second moon is up, then anyone with necromancy spells will no that. But if hippogriffs can be tamed with their addiction to coffee beans, then maybe nobody has learned that yet.
d. Most especially, tell them any house rule that might affect character creation.

15. There must be enough rules consistency, and world consistency, that the players know what they can count on.
a. They should also know what they cannot count on. It’s OK for your goblins to be different from the goblins in the rules. It’s OK for them to not know what goblins are like. But it’s not OK for them to believe that goblins will be rules-goblins.

16. When you change rules, you don’t necessarily have to tell the players the new rules, if it is something that their characters wouldn’t know. But you should tell them not to assume all D&D rules apply.
a. If you changed dragons because most people in that world don’t know details about dragons, you don’t have to tell them those details. But you should tell them that dragons aren’t color-coded for their benefit.
b. Not knowing about the monster is a challenging adventure of discovery. Knowing things that are false is just a failure mode. No resemblance.
c. Changing rules has consequences elsewhere. Think them through in advance. If dragons aren’t color-coded, what does Tiamat look like?

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56. No matter what the game rules say, no matter what this document says, don’t do nothin’ stupid.
a. Exceptions exist. They do not invalidate general rules; they modify and limit them.
b. Some of these rules obviously don’t apply to certain games, or certain tables. Don’t apply them in those games.