Well when there is no money left I doubt you can save some But a good practice is always think like you have no money left even though it's not true this way you will spend less.
There are numerous ways to save money if you spend all of it:
1: sell you unnecessary things
2: if you have nothing to sell then give them smile as it is more precious than money.
* sell stuff
* stop unnecessary spending
* walk
* look for a way to make extra cash easily, like helping your neighbor or something
* use your credit card (if any)