Remember that tangent is sine over cosine. To start graphing, its helpful to make a table to see where your points are going to be like seen below.
The undefined part meant that the graph does not touch like shown below. Instead the asymptotes go at π/2, 3π/2, 5π/2, etc. (they also go in the negative direction like -π/2, -3π/2, etc)
Because sine and cosine are positive between zero and π/2, the graph slides up the asymptote. Between -π/2 and zero, sine is positive but cosine is negative, causing the graph to curve downward. While drawing the graph, keep in mind that the graph will never touch or cross the asymptotes, EVER!