Every 23 hours in Mafia Wars you can get an energy pack which takes your total energy to 125% of your maximum total. Since you can only get these once per day, you should take advantage of it. Here are a few different scenarios that involve the best way to use your pack.
Scenario 1: Collecting Consumable Items
To finish Mafia Wars New York, you need a lot of blackmail photos, concealable cameras, and untraceable cell phones. However, the “Rob the Electronics Store” job does not provide a very high amount of experience points for the energy cost, which makes it very hard to level up off of this job. However, with an energy pack, you can start off a fresh level by spending all of your energy on the “Rob the Electronics Store” job, and then use the energy pack and easily level up with that extra energy boost.
Scenario 2: Fighting a Boss
If you have a high-energy account, you can use Boss Fights to make the most of your pack. After using your energy pack, spend your energy until you are almost about to level, but stop doing jobs just before you level up. Now, go back to the Enforcer tier in New York and do the boss fight there. Now, when you level up, you will be able to start off your new level with a lot of free experience points carried over from the previous level.