if you use the 50mm f1.8 lens, and take a portrait at close range (subject fills almost the whole frame), using f1.8 the depth of field is very short. Even the entire head can't be in focus. But as long as the eyes are in focus, the portrait looks very pleasing. I dunno... that's just my opinion from my trial and error
Put down that photography guidebook, get off the internet, and head out of the house. Talk to everyone and anyone that interests you. Find out what it is that makes them tick, get under their skin, step into their shoes. Then take that camera out and shoot away.