Asymptotic growth of functions

How to determine if a given f(n) and g(n) is in theta, omega, big oh, little omega, or little oh.

- I think one way of doing it is by plotting graphs of both functions f(n) and g(n). Even by plotting graphs how do we say when a f(n) is in theta, omega, big oh, little omega, or little oh? Am not clear on that. Can someone throw more details on that?

Also I am not sure if this is the correct way. Can anybody tell me if there is any other simpler way of doing this.

Say example:1. f(n) = sq root(n) and g(n) = n^sin n

2. f(n) = 1/square root(n) , f(n) = 1/logn