Below are listed more advanced tactics to winning battles. A player should understand most of the Battle Basics before reading these.
Power = Win
Half of your problems can be solved with leveling up. The other half of your problems can be solved by properly abusing the Item World, Specialists, Reincarnation, Master-Pupil Relationships, and basically doing anything to get your stats as high as possible as fast as possible. A Lv9999 Adell with 300 Felonies, perfect equipment, and an army of pupils can smash anything it wants to tiny little pieces. ANYTHING.
The only other problems you might run into can be solved with patience and luck. Question: How many times must I drill through the Item World before that last Pirate finally shows up? Answer: Patience and luck.
Supporting Cast
Alright, so the afore-mentioned Lv9999 Adell kicks ass. With proper support, a Lv3000 Adell can kick just as much if not more ass.
No party is complete without a healing unit, a Cleric's or Beastmaster's stat-boosting abilities, and a Thief's status-infliction. A Cleric's healing and stat-boosting spells can be reincarnated and pupil-taught so many characters you have can learn some level of them (although obviously not everyone can use healing spells as well as a Cleric); Not only will doing this make it so you can always spare someone to waste their turn healing the injured, but when it seems all a character can do for a turn is move, you can use Braveheart or Shield to boost their stats for the next turn.
Don't neglect innate abilities either: positioning a Beastmaster next to a monster can boost all the monster's stats by a huge 20%, but positioning three Beastmasters next to a monster can increase its power to 160%! (And that's not even using a Beastmaster's stat-boosting spells!)
Status Ailments
Sleep and Poison are beyond valuable. You can toss all foes onto each other until there's only one left with a brutally high level, then put him to Sleep, then Poison him. Each turn of poison brings down his HP by a whopping 20%, so in three or four turns you can finish even the toughest character off by using all your characters in one massive combo.
Throwing Tactics
Whenever you're throwing a character, always throw them before they move. This way the character can move after they're thrown, and get into new spots more easily. You can throw a character on top of a lift-tower, if the current topmost can lift, no matter how high the tower may be.
If you throw multiple foes (except Prinnies) on top of each other, their levels will combine.
You can use Heavy Knights or other defensive units to lift delicate mages out of the brawl for a while. If you're fighting a single super-powered character, who can kill any of your units in one or two hits, you can sacrifice a weakened lifter to save a more important ally from being killed off.
Base Panel: Why it's Awesome
Whenever an ally enters your base panel, two things happen:
- They disappear from the map, allowing you to bring out someone else in their stead. This is amazingly useful in the Item World, as you can send out a weakened character, then bring them back when most of the enemies are incapacitated so you can take your timing healing them.
- If they haven't attacked, you can bring them out again, with their move command completely refreshed. This can be used to extend movement range up to double normal amounts.
Even if a character has attacked and moved, you can still throw them into the base panel to get them out of harm's way. This is invaluable for mages or other characters who can bring down hell upon your foes, but can't be bothered to survive a single hit. However useful it could have been, you can't throw towers into the base panel.
Enemies can't stand on or walk through your base panel, but your characters can. You can use the panel to retreat behind after attacking, then your foe won't be able to approach you. This of course only works on foes with low enough MV, and without range attacks. You can use other tactics around the panel, but as enemies become stronger and more likely to have high-ranged specials, this aspect of it becomes less useful.
Weights
Weights seem pretty useless. Just one drags your character down to 25% HP for a tiny stat bonus (two bring it down to 6.25%, and with three your character might as well be dead). The trick to them is, they bring your character just into "Critical" range, which activates most characters' innate abilities.
While a Ninja doesn't have much HP or DEF, his SPD is incredible, to the point where he can evade just about anyone lower than his level who isn't using a gun. Now imagine that with his innate ability, which increases his SPD even further. He might as well be on an invincibility panel, 'cause no one will be able to touch him.
What's better, their HP will still be reduced to 25% after you remove the weight, so you can equip a more valuable item in its place. Just put the weight back on if you plan to heal them.
Abusing the Game
Disgaea was always made to have its systems abused on many different levels. A quarter of the game seems to be spent trying to find new ways to do it, but some players are opposed to these methods.
Move-Canceling
It's common knowledge that you can move a character, then cancel that move with 
. This seems simple enough, until you remember Team Attacks and certain Innate abilities.
You can move three Beastmasters next to a Dragon, then have the Dragon attack using the team-attack support and immense 75% stat boost of the Beastmasters. But now you can cancel all three of the 'Bmasters, then move them out to support another monster. Rinse and repeat. It's easy to see how amazing this simple gimmick can become.
Temporary Equips
In the middle of a battle, you can trade a character's current equipment with anything in the item bag, without using up the character's turn. A horde of obvious options instantly come to mind: changing to nothing but glasses against a Ninja, or nothing but armors when you're waiting for Poison to finish off your opponent.
But there's one that always comes in handy, even if it is a little time-consuming. Before moving, equip three shoe-type items to a character, move them with their hugely boosted move range, then return to their default equipment. Since the shoes are taken off afterwards, you can do this with every single character.
Unfortunately, there is a drawback to this. Lovers can only appear on an item when a character leaves that item equipped for a long time. Constantly removing and re-equipping items forces the counter to start over, and if you use this strategy on all your characters, the only lovers you'll ever earn will be on armors/ect items.
Diagonal Throws
Normally you can only toss a character in one of the four cardinal directions, or at least it seems that way. Notice that whenever you switch between two directions, the cursor slides diagonally between the two points, instead of just reappearing at the new point. With the right timing, you can throw a character diagonally wherever the cursor lands. It's easier to do with greater throw range, since the cursor takes longer to move.
Although this seems nearly useless, as you can't pinpoint where you want the throw to land, it can become invaluable on a screwed-up Item World stage.
Throwing Through 'No Entry' Tiles
It is possible to toss a character through a No Entry tile. Place your thrower adjacent to the tile you want to cross, target the tile immediately on the other side of the No Entry tile, and then shorten/lengthen your throw distance repeatedly while attempting to throw. There's a sweet spot between your thrower and the target tile where the throw will actually occur. You'll hear a few failure sounds and, with luck, should succeed at the throw after a few seconds. This trick only works if the 'No Entry' field is one tile thick. You can't throw across multiple tiles.
This trick is not a bug. One of the townsfolk in Holt Village will subtly allude to this trick during one of the later chapters in the game.
Lv9999 Nekomata Trick
In The Red River in Chapter 4, Axel's scheme has Geo panels that level the enemies by 10% after every turn. After several turns (nearing the hundreds) all enemies on the map will be level 9999. Do enough damage to a Nekomata, have strong characters inside the base panel and make sure that the character throwing the Nekomata into the panel is able to kill it (because the success rate of capturing monsters depends on those variables). If done properly, you will have a level 9999 Nekomata.