I am new to GMing , I have played Dark heresy once but the group got tired of it because it wasnt dnd 3.5. I am going to be running the new game with a group of new people. I have been studying up a lot and really only have a couple of questions. I am confused about characteristic bonus points. How to apply them and when. I have read it over and over again and dont understand. The other thing is insanity and corruption points, how and when to assign them. I understand the tables about mutations and and disorders and shock. but I am not 100% about handing the points out. Other than that I think I am good. Any help would be greatly appreciated.

This is coming from mostly a Rogue Trader perspective, but here it goes:

I assume by characteristic bonus points, you mean the characteristic bonus (ie, the tens place). The short, no duh answer is "its applied when it tells you to". More helpfully it's generally used in two ways, to calculate related values (like speeds, which are based on Agility Bonus) or it's used to add/subtract to relevant d10 rolls.

Insanity and Corruption are a more difficult issue. The rate of handing them out is isn't fixed, nor is there a 'perfect' rate. A lot of it will come down to what kind of theme and atmosphere you want the game to have. Handing them out more freely plays up the horror aspect of Dark Heresy, and reinforces the idea of things Man-was-not-meant-to-know. Characters in these games are as likely to be retired (or put down) from corruption or insanity as they are from being killed in the field. This is particularly good for very investigation heavy games with a bit warp component.

Handing out fewer will instead make the game more 'heroic' and shift the focus to solving investigations effectively/quietly/quickly. Threats to the character will come from physical danger (combat, environment) rather then psychological danger. This is often better for more adventurous games, and games that are human/xeno, rather than warp, focused.

Characteristic bonuses apply where the game says they apply. For most skills this is not important. Your Perception bonus is borderline useless, and unless you intend to run a medical ward, so is your intelligence bonus (though obviously it helps to have high skills). I'll give you the basic gist of what each characteristic bonus is used for:

Strength: Additional damage on melee attacks

Toughness: Damage reduction

Agility: Movement speed and dodge range (that is, if dealing with explosive weapons, if your agility bonus is lower than the blast range, it is impossible to dodge the blast).

Intelligence: Treating multiple patients with medicae over the long term. There's also a daemon in Ascension that has abilities triggered by his Intelligence bonus, but unless anyone in your party is a Lord of Change, this does not apply to them.

Perception: ....You've got me. No idea.

Fellowship: How many people you can affect with Fellowship with a single test.

Willpower: Usually for damage on Psychic powers.

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As a general note, your [characteristic] bonus does not modify your rolls. It is usually used in other tests.

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As far as insanity and corruption goes, Corruption is very rarely given out. Corruption is when the actual fabric of reality starts getting damaged and affecting realspace. For example, being at the site of a daemonic invasion will cause corruption. Seeing what's left of a Dark Eldar's torture victim will not. Other main sources of corruption are psychic powers and sorcery, though if you're the GM you can always cook up a few other sources. Just keep in mind, that it should involve influence of the Warp in some way.

Insanity is for basically anything else. Things that would mentally disturb the Acolytes. Being exposed to torture for extended periods of time. For example, in my own campaign, my character recently received insanity points for undergoing extensive surgery without anaesthetics of painkillers. Another time our assassin walked into a room where a former ally's internal organs had been used as decoration in the most visceral fashion and suffered insanity for it (though only after failing a willpower test).

Layman's terms: Corruption comes from the warp and is something that taints the individual's soul. Insanity comes from things that would rattle the mind of an Acolyte, whether from pain or horrifying visions. If you're clever about it you might even be able to do it with guilt-- such as if an Acolyte, by their own blundering actions inadvertently brought about a situation so bad a planet had to be exterminatus'd? I'd totally consider that worthy of insanity, from the guilt-tripping.

Thanks that helps a lot