You can use most generic flashes on any dSLR. They have the advantage of being ridiculously cheap. Aside from that, you gain total control over the amount of light thrown.
Generic flashes have only one electrical contact on its mount. Check that the voltage requirements of your camera is not lower than that of the flash before buying.
- Set the flash to Auto or Manual mode.
- Set the camera to Manual mode.
- Set camera to use maximum flash sync speed. If you don't know, use 1/125s to be safe.
- Set camera to lowest ISO then set the flash to that ISO too.
- On the flash, decide a range of distance (for flash Auto mode) or a specific distance (for Manual mode) you will be from your subject.
- On the flash still, see what aperture size is recommended at that distance.
- Set that f/number on the camera.
- Take a shot making sure your subject is at the distance you chose. Of course you can approximate.
- If the picture is too bright, make f/number larger. If picture is too dark, make f/number smaller.
Now you know!