If you are thinking about putting live plants in your aquarium it's a pretty good idea. The first thing you need to do is get a florescent hood. A florescent hood is very important. Most plants will not survive without a flourescent hood. You can't put it by a window or your tank could have major temperature problems.
Live plants are a very important thing to have in an aquarium. The live plants will help lower nitrate levels and they will also create a more natural enviroment for the fish in your aquarium. The live plants will need trimming every few months. Trimming the plants will help keep it from getting too big and obscuring your view of the tank and the fish in it.
In order to trim your plant you will want a pair of scissors of some sort. Make sure you use scisors that you can put in the water and make sure there is no oil or grease on the scisors. Depending on what type plant you have you may want to trim a little or alot. If it is a plant with a long stem and one leaf and you only have about 8 you may want to only trim a couple of the long ones. If you have a plant like mine which has several on each stem you will want to trim it to whatever size you think would suit it best.
When I trim it I have three things on hand scissors, a towel (to clean up any mess or to wipe your hands with, towel the carpet, etc.), and a bucket (or something to put the trimmed plant in). You can simply trim the pieces off the plant and put them in the bucket. Make sure that you do NOT leave any large pieces in the tank as their rotting may cause the nitrate, ammonia, etc. levels in the tank to go up and cause stress on the fish as well as you having to change the water more often. Some of the pieces may also sprout roots and grow another plant like the plant in my tank.