First of all, be sure orbital planes match up (are or really close). If they don't, the delta-v required makes it worth just launching again. When you've got an orbital plane matching the target, remember the simple rule first derived by Newton: "Equal areas in equal time." Or in layman's terms, the farther away you are, the slower you revolve around the body. The closer you are, the faster you revolve around the body. This also goes for elliptical orbits. If the target is behind you in the orbit, make yours slightly bigger (a short burn in the direction of your velocity), if ahead, make it smaller (a short burn opposite your velocity). If accelerating in the direction opposite the target feels funny to you, welcome to orbital mechanics!
You only need to do these burns once; this will leave you with an elliptical orbit, with one side more or less touching the target's orbit, and the other side below or above the target's orbital altitude. Now, wait a few orbits to catch up or for the target to catch up to you.
When the intersection is close enough, it's time to use the nav-ball at the bottom of the screen. When targeting a craft at close range, it tells you both the position of the craft (pink dot with circle for the craft, pink dot with lines for opposite direction from the craft), your relative velocity to it, and the direction of the relative velocity (the green circle on the navball). First order of business: reduce your relative velocity with the craft. For your first run, if you have enough fuel, reduce the relative velocity to 0, followed by approaching the direction of the craft slowly. If you are experienced or have low fuel, reduce velocity while redirecting it towards the craft. Slow down as your approach the craft; you should be using RCS at this point; so make sure to read the controls for the docking panel (at this point you should also switch from staging to docking mode). Now it's a matter of lining up the ports. Be sure they are very well matched up, then go in to dock at an extremely low velocity. The low velocity is extremely important, as it keeps you from bouncing off, and more importantly, keeps you from imparting much of a spin on the station if you accidentally bump it. A spinning station is damn near impossible to dock with.