Hmmmm.....
Well, there are a lot of stickes at the top of this forum that will give you a lot of information, but I was really confused at first too when I started planting a tank, and the stickies get pretty technical.
The basics of what you need are:
A really good light source. You will want to go with t-5s or PC lighting. You will need at least 2 WPG to get a really planted tank going. Anything less limits you on the kind of plants you can have (java ferns, anacharis, maybe some crypts or anubias)
A nutrient source. Most low light, low tech planted tanks rely mostly on the fish for fertilizer, but once you get over that low light threshold, you need fertilizers. If you want to go that route, post the kinds of plants you want, the type of lighting you have, and the size tank you have and we can help you set up an esitmative index fertilizer schedule.
Substrate: You will want a substrate for a planted tank. Look for Eco Complete, Flourite, Amazonia Aqua Soil. These soils are clay based and will help your plants root, and flourish.
Heater...Well, I use regular old glass tetra tec heaters in my planted tank. You can get fancy and use a substrate heating coil if you want.
CO2 source...Again, for the over 2WPG tanks. If your tank is small enough and you have enough time, you can do it cheap DIY with yeast, sugar, 2 liter or empty milk jugs, and either a power head or some other diffusion method (ladder, bell, filter intake, custom reactor)
Fish, of course
And plants. Look to plantgeek.com to find some ideas. It would help a lot to know what kind of plants you want, and specifics about your system.
Hope this helps.
