If you look under the composition preview panel (in normal workstation) there are some options about playback like how large (the percentage drop down box) and a little more to the left there is one that says different resolution presets (half, full). That allows you to render and play back faster (if you use a lower setting).
If this was not what you were trying to do there are alot of other options that you can change after effects with if you click "edit", "Preferences", then the topic you need.
If you want "realtime" playback, then you need to do a ram preview. If your material is not rendered then it will not play back in realtime.
Also, you are obviously using the wrong render settings, but without knowing what your composition specifics are and what you are trying to render out to, then none of us can really help you.
I recommend reading up on beginner After Effects a bit.