Welcome. Praise the Lord. The fact that you opened this page, gives us hope that you like to be involved. 

Our low profile Local Body of Christ (LBOC) ministry number 1. door-to-door ministry to connect Christians with each other.
What you need: A6 paperbook (it is small and fits in a pocket) and pen/pencil to write down addresses.
Factors in deciding which location:
-Your available funds and time are important considerations. The expected number of Christians and which denominational background of most Christians is another consideration.
-Housing situation: It makes a difference if you do this in the countryside where houses are far apart or in a city in a high rising apartment block. Semi-detached houses or a villa quarter. All are considerations. In a flat, you will normally use an intercom instead of being at somebody's door. This is generally more challenging.
How to divide an area (city/town/village/neighbourhood)
Whatever you choose, you need to go to all homes in that area till you have found at least 2 homes with interested Christians. The maximum would be 20 homes with interested Christians. To explain this with housing numbers: a village with one thousand people with a population of 2000 people and an expected Christian population of 500 people (25%). This village you can divide in a maximum of 500 (expected number of Christians)/20 (actual number of homes with interested Christians)=25 localities. When there are less interested Christians, it means that on average the interested Christians live further away from each other and you will have less localities to do ministry in.
administration: you can do this in two ways. For both ways you write down the street plus city/town/village on the top of a new page.
intensive: visit each home up to 6 times incase nobody is at home
use abbrevations: nh=not at home. c+i= Christians and interested,. c+ ni: Christians but not interested. nc: after having spoken to somebody from that house it is not clear whether there are Christians living or not. After each abbrevation you write down the housenumber if any. If no housing number, the name of the house. if no name of the house, you need to give each house a number and draw a map of the locality where you are doing ministry yourself so that you know which house is which. Each time you revisit a home where nobody was at home, you should do so for all homes in that locality. Then you can give that locality a number of total visits. Where nobody was at home, but now there is, you 'scratch' the number from nh and list it under the relevant heading (c+i, c+ni or nc). For intensive you divide the page top down in parts. nh near the top. below (allow a lot of space as many are not at home) for c+i. allow space below and then c+ni. allow space below and then nc near the bottom of the page.
not intensive: only visit each home you only need: C+i.
What to say at a door: You introduce yourself with your own name and that you are part of Local Body of Christ ministry (say full name at least to new people). You say that you like to get in touch with all Christians in this neighbourhood but that you don't know where they live. you then ask: Are there Christians living at your home? if they answer, you say that you like to connect Christians in the neighbourhood with each other. You also say that once you have contacted all Christians that you will get back in touch to explain more. If they don't object, you can regard them as interested Christians at first. if they object, then you thank them for their time and they are then Christians but not interested. Once you have contacted all Christians, you get in touch again with all the Christians who were interested and you give them on a paper each other's addresses. You also share those two Bible verses:
 Matthew 18:20 NIV: "For where two or three gather in my name, there am I with them."  Hebrew 10:25 NIV: "not giving up meeting together, as some are in the habit of doing, but encouraging one another - and all the more as you see the Day approaching." 
For the intensive approach, that's it. For the not intensive approach: it is the same but you will reach this point much quicker as you only wrote down the homes of Christians who are interested and visited each home only once where nobody was at home.
how to decide who is and who isn't a Christian: your question was: Are there Christians living at your home. if they say yes, you believe them in principal. If they say no but they do say other things which makes it clear for you that they are Christians, you also consider them Christians. e.g.: Are there Christians living here? no, we are Catholics. (meaning Roman Catholics). Roman Catholic is a Christian denomination. They are Christians therefore.  If they say they are Christians but they say other things which makes it clear for you that they are not Christians, then you don't consider them Christians. e.g.: Are there Christians living here? yes. we are Jehovah Witnesses. Jehovah Witness is a Christian sect from the standpoint of mainstream Christianity. A Christian sect has Christian influences but is different from a Christian denominiation in that people in a Christian sect are not Christians but people in a Christian denomination are Christians. Jehovah Witnesses don't agree with the view that they are a Christian sect. They consider themselves to be Christians and they regard the so-called Christian denominations like Roman Catholic, Presbyterian Church, Baptist Church, Assemblies of God as Christian sects. There might be Christians in those denominations but only as long as those Christians don't subscribe to the faith tenets of their denomination. It comes down to whether you consider a Jehovah Witness a Christian or not. If you do, fine. you include them in the list of interested Christians. If you don't, fine too. You don't need to write down anything then as you only write down those who are not a home, those where it is not clear whether Christians live there and those homes with Christians (interested plus not interested). If you are in doubt whether a person is a Christian or not, then it is up to you do decide to put them on the list of Christians or consider them as unbelievers.
extra: As described above, that is our low profile ministry. We just help Christians to get in touch with each other. The extra's are that you might have nice conversations with any of those you met. Be flexible as that happens. Keep in mind too what your purpose was so keep an eye on the time and the available time or date by which you want to finish the project for that locality. If you continue to actively help those Christians to get in touch with one another, you are not doing our low profile ministry anymore but you are involved in planting an organic housechurch which is either ministry two or three. Other ministry rules apply for that and because of that, it is important to know clearly what you want to achieve while doing ministry in a certain locality or to be flexible to move on to try to plant an organic housechurch if the circumstances give opportunity for that. As other ministry rules apply for that, you have to check if you think you have a chance to meet those requirements before you allow yourself to get actively involved in that. If you don't, you risk that you cause problems in the area of sectarinism and bad leaders in your absence (after you left them). We don't want to be hold accountable for that in LBOC. Therefore you have to check if you think you can meet the requirements for planting an organic housechurch.