How to design the rectifier??
In my own personal experience in making power supply during my college days as an Electrical Engineering student for 5 years, i found out how rectifier serve as the most vital part to take considerations in our practice. 
To make a rectifier you should first know the ideal applications that you intend to use it for. In my case i am always using a bridge type full wave rectifier. This is a reliable design to have a stable DC output voltage. But, as always we can never do a 100% purely DC supply when using a transformer so basically it always came with a bit of pulsating currents unlike those dry cells which is capable of producing a straight line voltage. Going back, if you are trying to use the rectifier in a circuit that contains a sensitive ICs and other electronic elements, you better add lots of capacitor to filter your output more. If you are a beginner, make use of a 1n4001 diode great for forward biasing and suitable capacitance 1000uf or more to filter the output line. All in all the trick in making a rectifier lies behind how you play the diodes and capacitors along in the circuit. I hope this very simple circuit may give a little answer to your question, just follow this link https://www.google.com/search?q=nerd+engineer+pictures&amp;biw=1366&amp;bih=696&amp;tbm=isch&amp;imgil=Pi5Y-Z4DXHSloM%253A%253BoZ8FFdMocjQElM%253Bhttp%25253A%25252F%25252Fwww.affinite.com%25252F&amp;source=iu&amp;pf=m&amp;fir=Pi5Y-Z4DXHSloM%253A%252CoZ8FFdMocjQElM%252C_&amp;usg=__hvC2NRRseMWHzueK3mBYuyOD284%3D&amp;ved=0ahUKEwjUkpum9MPSAhVG0YMKHYamAH8QyjcINw&amp;ei=UWa-WJSmNcaijwSGzYL4Bw#tbm=isch&amp;q=bridge+type+rectifier&amp;*&amp;imgrc=yidbnb0eK_wGWM: Hope this helps.