Species would be great, but i'll mention a few basics that hold true for *most* species.
~10gal per specimen or two. The more water, the less you need to change it or worry about ammonia and nitrate build up. Also, space is important to keep animals happy and healthy.
A haulout; that is, something that allows the newt to get out of the water. Depending on the species the size and setup will change, but most newts like to get out of the water sometimes.
Aquarium decorations: I prefer live and or plastic plants, driftwood, and rocks, but really anything will work as long as it is aquarium safe. The newts need someplace to hide.
Filter: I like filters, some people don't. For most tanks a small charcoal filter attached to an airpump works just fine.
Depending on the species you will need to take into account food and water temperature. Some species will accept larger foods like pinhead crickets, small insects, etc; smaller species will probably need blood worms, black worms, etc; all of which can be purchased at a local pet or fish store.
Once you find the species or have a description you should post it so we can direct you towards more detailed and specific information.
Best of Luck,
Alex