One of the most peculiar parts of Paraguay is how to "knock on the door." Some houses have buzzers, which you can press and usually hear ringing in the house. But, this takes away all the fun. The usual way to "knock" is to clap.
I don't believe there is any particular method to the clapping. Some are louder than others. Some people clap three times to announce their presence at the gate and others keep clapping until someone comes out. Usually friends clap a few times, but venders, as you can imagine, clap until you come and talk with them. As you can imagine, when you live near-by to other houses the claps get hard to distinguish. Many times, we will go outside assuming the clap is for us, but only to find that the clap is for our neighbor.
I think by the time we are here for 5 years or more, we will know the distinctive clap of people that are outside our gate and beckoning only our family. Then we will know that we have arrived. Personally, in order to help others with this potentially confusing problem, I (john) like to put a little boogie in my clap and usually try to tap out a "funky beat." :)