Disgaea: Hour of Darkness Hints

To level your weapons faster, go to the level Terrible Cold in the area Jotunheim (it should be the one with invincibility on all the panels except for one). Make sure you have a character with a high amount of counters(the ninja class or the majin class) a strong person who could kill a level 100 person, and the person you want to master the weapon. First, start by throwing all the enemies into each other. Then when they are all combined, have someone pick the enemy that you just made and hold em. Next, have the ninja or the majin and the person you want to level up come out and have them beat each other up. If you did it right, your team members should be beating each other up with regular and counter attacks. Just do this for as long as you want. Each hit raises their weapon mastery. To speed up the process you could go to the item world and get the armsmaster specialists and attach them to a weapon, so your character levels faster. When you are done levelling, kill the enemy that you were holding.

If a character is about to attack an enemy, you can move other characters around the attacker and you will preform a Team Attack as you normally would. Execute the attack then move the cursor over the supporting attackers and press circle. The character will move back where it was. You will be able to move the character normally as well as preform a normal attack (or a skill).

This is an easy way to squeeze more damage out of attacks without having to waste turns.

If you unequip your attack/defense/other items and then equip movement items (shoes, hyperdrive, ect.), you can move very far, and before you attack you can re-equip your other items, and it wont move you back. Now you can attack with your re-equipped items. Just repeat this on your next turn.
Now you can move really far without sacrificing defense or attack damage. This is also useful if you have only a few movement items (especially hyperdrive), since you are un-equipping it every time you use it, your other characters can use it too.

When you beat the game, stay after the credits and you will be asked to save. Save and reload then you will be able to start the game with your old stats, items and characters (except storyline characters).

When you try to pass a difficult bill at the Dark Assembly, the only option normally available to you is to kill all of the opposing senators simply because it's nearly impossible to get a difficult bill passed legally. But who wants to constantly get into fights in which they're massively outnumbered by high-level enemies?

Here's a nice trick to bypass the entire process. Before choosing to begin the vote, bribe a high level senator in the front row. Make absolutely sure he's on your side, then begin the vote. After the vote fails, choose to persuade by force and take a bunch of characters with long Throw distances into the battle. Rather than having to fight off a ton of senators, you can simply throw them onto your mole in the front row! So long as the level of the senator you're throwing is less than the senator doing the catching you'll be fine, and after throwing a couple of senators at the mole, the combined levels will be so high that you won't need to worry about levels at all.

Repeat this process until all of the opposing senators are gone, and you avoid having to fight any of them. This is an excellent, cheap way to unlock a lot of bills well before you should be able to do so.