Making AC to DC??

I am wondering if there is any information out on the web or maybe
from someone here about the hows and rules in making DC power
supplies?

I guess my question is if I know what DC volts I want and I know what
Amps I want, how would I build a power supply to do this?

Is there some formula that tells you the size of transformer, Bridge,
cap, and what ever else you need?

Thanks

Jeff Davis.