What everyone said is correct. Essentially, many ways to aschieve the same result. It all depends on what you find easier to contro, and use in a real-life situation.
Generally, if I have the lux of time, I go all Manual on cam and on flash as that would give me total control. The advantage of going fully manual is also that you tend to be more mindful of apeture settings, especially important in portraiture work.
Depending on what you want to achieve in the photo:
1) Overall balance - correctly exposed BG and correctly exposed face : Meter for BG (with shutter speed set at or below max sync speed), and set the flash on M according to what distance you lens tells you and what apeture you're using. Adjust M flash output accordingly after previewing results.
2) Dark BG, correctly exposed face : Meter for BG, then either increase shutter speed (up to max sync speed) or decrease the apeture or both to get the BG underexposed. Set flash to the correct M setting according to the flash to subject distance, and apeture opening to expose the face correctly. Adjust accordingly after previewing.
This is just a guide to get you started. Don't be afraid to break the rules once you've learnt them, but not before. LOL! Also, as with any guides, explore variations of the basic settings to see what gives you the most desirable results. Often, you will find yourself deviating from the 'norm' for best results, and that's perfrectly ok.
For stress-free practise, try using a doll or inanimate object. That way, you won't be so kan-chiong ... esp in fron ot a chio bu.