Successfully complete the game one time, then start a new game to have 250 promotions available.
Getting promotion points
You can get Promotion Points (PP) by doing the following:
Completing a level: 1 PP
Keeping all of your pigs alive in a level: 1 PP
Completing all the levels on a island: 5 PP
Completing special tasks on some levels: 1 to 5 PP
Easy kill
This trick only works if you have Freeze Gas and Hide. First throw Freeze Gas on your opponent(s); then Hide for as many rounds as necessary for the opponent(s) to sneeze themselves to death. Even the strongest opponent (legend) can be defeated in this way. However, this may take up to (150-15)/10 i.e. 14 rounds; weaker opponents are finished off sooner. The advantage of this method is that even if you are outnumbered and/or very weak you can still kill really strong opponents while guaranteed that you get away unharmed.
Destroying vehicles, pillboxes or artillery
When you are attempting to destroy vehicles, pillboxes or artillery, an excellent way to do so is to have a pig with a flamethrower (Pyrotechnics have them, level 3 heavy weapons soldiers, or they can be used in multiplayer mode). Walk it up close to the intended target. Face the target, and let rip with the flamethrower, so all the flames hit the vehicle, pillbox or artillery. It should suffer about 102 to 108 points of damage.
Attack with jetpack
If you have jetpacks that you do not need, walk up to an enemy and turn around so you are facing directly away from your target. Equip a jetpack, and aim directly upwards. Fire the jetpack, and then release it after about two seconds. The enemy will suffer a maximum of 20 points of damage from the blast caused by the jetpack hitting the earth, plus any additional damage caused according to where the pig lands. Your pig should land safely by parachute, but try and make him land on an enemy. If you can do so, you will inflict 1 point of damage. You can repeat this as many times as needed one turn, providing you have enough jetpacks and do not suffer damage yourself -- using a jetpack does not end a turn.
Get Commandos before the level 1
Select a new game. Name your team WATTA PORK, then play the training mission. After the loading screen you will see two FMV sequences. The game will return to either the start-up screen or the men upgrade screen (depending on the version). Select multi-player and choose a death match. Select the Play Pen level, and choose all your men as paratroopers. Start the game and you will see the FMV sequences again. The men upgrade screen will appear, and all your men will be commandos.
Swimming
Commandos and Heroes are the only ones that can swim without losing health. All other Pigs will lose health trying to swim.
Hiding place
If you find a "?" box, this may be one of the Pigs hiding. This will not appear on the mini-map.
Destroy bridges
To destroy a bridge, set TNT or Super TNT on it to blow it up. Note: This may not work on all bridges.