Like most players, you probably have the Personal Income Tax as your main money maker (unless you rely on tourism). How do I make more money from this without raising my taxes and lowering my approval rating? You could have your population grow and keep their GDP (Average Income Divided by Population) the same or go the faster way and hit the GDP straight on.
There's only one thing that affects your GDP.
How much you Import and Export.
For every Million dollars you have in surplus/deficit in your trade bar, you gain/lose a thousand dollars in GDP, this rule does not apply to illegal sectors. You want a surplus in all areas to maximize your GDP. Increase production if you have the cash, if not, do everything you can to climb out of debt (you can also use the "Assume my Debt" treaty on rich countries, like USA. note: this will only work if you have good diplomatic relations with the other country; 80+), and then start investing. Doing this once will not solve the problem, you may need to increase production ten times before you get it to a not loss/gain moment, leave it there, and invest in other sectors. Work from the top of the list to the bottom, the reason is explained in the Resource Importance and Dependencies section of the Economic Resources page.