How do the stewards of the federal government in America plan their budget? It’s not a trivial question to answer.
The President submits a budget proposal for the upcoming fiscal year. Congress, both House and Senate concurrently via the House and Senate Committees on Appropriations (in turn divided into 12 subcommittees), then proceed to draft a budget resolution. It is not considered a bill, so it is not presented for a presidential signature, nor can it be vetoed. It passes on a majority vote. There’s about 19 different budget functions, i.e. spending categories. Approx. 63% of the federal budget is dedicated to mandatory spending, including most entitlement programs, which aren’t even subject to appropriations — it’s just a public obligation.
Various hearings are scheduled, taking comments from experts, officials and perhaps laymen, too. Adopting the resolution then sets in motion various mechanisms for enforcement — discretionary spending caps, the statutory cap (a requirement that if an appropriations bill exceeds statutory limits, a sequester order must be issued by the President cutting all discretionary spending by a uniform percentage — we’re talking values like 0.0013% here; there’s no starving this beast!), and so forth.