Depends. It can be good to cycle the tank before adding plants because ammonia plus light can lead to major algae out breaks. With live plants, cycling with low/no light is not an option. On the other hand, live plants can help break down ammonia, so can actually aid the cycle. I opted to cycle my first tank with plants. I started the tank off pretty heavily planted and added fish extremely slowly, and it worked very well for me.

Also, if you are new to planted tanks, choose your plants carefully. Some plants are very particular about light, fertilizers and CO2 and it can be very discouraging when they all die off. Let us know if you want some suggestions for easy to grow plants.

"Hi everyone. I am relatively new to fish keeping. I am just wondering how to start a planted tank and how long to wait before adding some plants to it. I will post some pictures on here when I get home. Also, how should I position them so that the fish get all the space and security that they need. "

I like to position the plants in bunches, so that the fish can swim in there and hide when they don't want to be in the open space of the tank. How your fish want the plants depends on the type of fish. Some fish need dense planting to feel comfortable; my Elassoma gilberti are an example of this.
Planted tank ideas from the Aquatic Gardeners' Association aquascaping contest: http://showcase.aquatic-gardeners.org/2010/index0a.html

I do not have any readily available data on how live plants affect the growth rate of nitrosomonas and nitrospira bacteria (the time required for the tank to, in the traditional sense, 'cycle'). I do, however, have other information you might be interested in:
Information on the bacterial nitrogen cycle with a real time line as to how long it takes: See slide 8: http://www.ag.auburn.edu/~davisda/class ... Design.pdf Information on how to cycle without using fish: http://www.fishkeeping.co.uk/articles_5 ... rticle.htm
You can see that if your average person with an unplanted tank waited "a week or two" as recommended by someone else on this topic, that would place them squarely at the point when toxic ammonia is at its highest concentration. "A week or two" with only bacterial ammonia processing would kill your fish. 35 days are required to fully cycle an unseeded tank. I personally would wait 40. However, "a week or two" in a planted tank is very different than in an unplanted tank. Here is the reason why:
Information on how plants eat ammonium and nitrate to grow: http://theaquariumwiki.com/Plants_and_B ... Filtration (More information in Diana Walstad's book, "Ecology of the Planted Aquarium")
This data suggests that because plants remove ammonium from the water column, live plants can replace nitrosomonas and nitrospira bacteria as an alternative nitrogen cycle of sorts. Such data as posted there supports Alasse's advice to add plants right away to new tanks.

But more on that later. First I will give you a step by step guide to answer your other question: how to set up a planted tank. Personally I use kitty litter as the substrate in my planted tank because I like how it doesn't need a capping layer. If you were to go that route, you would
1. add the kitty litter (pick a brand with no added clumping chemicals or fragrance, just clay, and put it in your tank)
2. add an inch or so of water
3. pack the kitty litter down with your hands
4. add more water. Be very gentle; you might want to put a deep bowl in the tank and pour the water into that instead of onto the substrate. If you pour directly on the substrate, the water will be cloudy for a day or two.
5. bury the plant roots. I like to use 10 inch planting tweezers for this, and they're only $5 on ebay. You don't necessarily need them, but they're more precise than fingers and make your life easier.
6. add fish flakes every day as if there were fish in the tank but without fish in the tank
7. if you have no test kit, wait forty days. Or, if you have a test kit, measure ammonia, nitrite, and nitrate, waiting for ammonia and nitrite to rise initially and then fall back down to zero. At this point your tank would be fully cycled in the traditional, nitrosomonas and nitrospira bacteria sense.
8. after ammonia and nitrite fall back down to zero ppm and nitrate is nonzero, finally add fish.
9. continue monitoring nitrate with your test kit, performing frequent periodic water changes to keep nitrate less than 30 ppm in concentration.

Now: The plants may or may not be able to completely handle the initial ammonia spike. New plants can go into shock and take even a month to be able to recover and start absorbing ammonium. Or you could simply have not added enough plants to be able to absorb all the waste. If you do not have sufficient plant mass or they are quiescent instead of actively growing, your planted tank could indeed have an ammonia concentration.
However, it is also possible that the plants adapt immediately to your water conditions and begin growing the moment ammonium is present. During steps 7 and 8, this large mass of growing plants may eat all of the nitrogenous waste from the rotting fish flakes you are adding every day, and you would not detect a measurable concentration of ammonia. Such a tank is 'cycled', just with plants instead of with bacteria. You should measure the ammonia with a test kit to see whether or not your initial planting was sufficient to overcome the production of ammonia.
In the long term, some tanks are planted heavily enough to not need bacteria. Some tanks are planted only lightly enough to help the bacteria, but the bacteria is still necessary to convert ammonia to nitrite to nitrate. That's why a test kit matters. If you detect ammonia as shown in the timeline in the nitrification pdf I posted earlier, then the plants in your tank are not able to eat every last drop of the ammonia and you still need to rely on a bacterial population to convert ammonia to nitrite to nitrate.

Information on what to look for in a substrate for a planted aquarium: http://www.thekrib.com/Plants/Fertilize ... jamie.html
If you use soil from your backyard capped with a few inches of gravel, usually the tank is instantly cycled because of the beneficial bacteria that was already living in the soil when it was out in your yard. If you use a sterile or not-seeded substrate like bagged store bought gravel, sand, kitty litter, or Fluorite(TM), usually such an 'unseeded' tank takes about 40 days to cycle. Such a tank can be 'seeded' with beneficial bacteria by adding a sponge to its filter taken from a second, long established aquarium. The cycle in these seeded tanks can range anywhere from being instantly cycled to requiring the full 40 days, depending on the number of beneficial nitrosomonas and nitrospira bacteria that survive the transfer from one tank to another. Keeping the filter sponge wet while transporting it between tanks will keep more bacteria alive during transfer.

Here's a link to my blog-type topic, so you can see an example of what a kitty litter substrate looks like: http://forum.nanfa.org/index.php/topic/ ... e__st__760
Direct link to the most recent video of the full tank: http://www.youtube.com/watch?v=RTA7y9Tns5M
Lots of other substrates are viable, too; you don't have to choose kitty litter just because I did. Just make sure to pick one that has nutrients like iron, magnesium, and calcium in it. Pea gravel is pure silicon dioxide and may not be the best choice.