At which age should I start talking to boys ?

i want to know at which age should I start talking to boys to envisage a relationship that could lead to a marriage?

Walaikum Assalaam Warahmatullahi Wabarakatuhu,
Marriage is not something to throw yourself into all by yourself. Getting the help of someone, especially parents, relatives, an Imam, and/or respected and trustworthy members of the Muslim community to either look for the right spouse or initiate and participate in a communication process is very important.
Involving others, by the way, does not mean signing over your right to say yes or no to a marriage proposal. It simply increases the likelihood of finding out important information about a prospective partner in a way that maintains rules of Islamic modesty (i.e. not meeting alone, see next point).
Getting that third party involved also helps verify if the person you are interested in is decent, honest and respectful. This person(s) often checks out references, asks about the individual’s character and behavior, and looks out for your best interest in general.
This person should be a trustworthy Muslim, since you are seeking a Muslim in marriage, and would want someone familiar with the Islamic way of doing things.
For those blessed with Muslim parents, remember that they are probably your best allies and helpers in seeking the right husband or wife. They have known you all of your life, and have your best interest at heart.
However, parents must be open and attentive to what their children are looking for, and never forget the element of choice. Ultimately, it is their son or daughter who is going to make the final decision. They must never become too pushy or aggressive, whether this pressure is being applied on their own son or daughter, or on the person s/he is interested in.
If parents, other family members, an Imam or members of the community are not available, you can also try seeking a husband or wife through the matrimonial services offered by a number of different Muslim organizations.

Always ask for references
This is also where your “third party” comes in handy. Not only will they be able to be your reference. They can also check out a prospective mate’s references.
A reference can include an Imam who knows the brother who proposed to you, a sister who knows the woman you may want to marry well, a family friend, a boss, a co-worker, and/or business partner.
A note about honesty and references: the people you ask may know something not very nice about your prospective spouse. Remind them that if they reveal this information, they would not be backbiting from the Islamic perspective. In fact, in the case of seeking marriage, complete information should be given about an individual, both good and bad.
The advice of one of the companions of the Prophet, Umar Ibn al-Khattab Radi Allahu Ta’ala Anhu, can help in this regard:
A man came to Umar ibn al-Khattab and spoke in praise of another. Umar asked him: “Are you his nearest neighbor such that you know his goings and his comings?”
“No.”
“Have you been his companion on a journey so that you could see evidence of his good character?”
“No.”
“Have you had dealings with him involving dinars and dirhams [money] which would indicate the piety of the man?”
“No.”
“I think you saw him standing in the mosque muttering the Quran and moving his head up and down?”
“Yes.”
“Go, for you do not know him…”
And to the man in question, Umar said, “Go and bring me someone who knows you.”
(quoted from Islam The Natural Way by Abdul Wahid Hamid, p. 66)
This gives you three types of people you can ask about a prospective mate’s character: a neighbor, business colleague or someone who has traveled with them.
When you meet, don’t be alone
The Prophet said: “Whenever a man is alone with a woman the Shaytan makes a third” (Tirmidhi).
He also advised men: “Not one of you should meet a woman alone unless she is accompanied by a relative within the prohibited degrees” (Bukhari, Muslim).
When you speak, be businesslike and to the point.
The purpose of meeting and talking to each other must also remain within Islamic guidelines. That means no flirtatious speech of a sexual nature on either side.
Imam Nur Abdullah says some of the topics discussed can include each other’s interests, financial situation of the man, who is Islamically responsible for providing for his wife and children, and the two potential spouses’ relationship with their parents.
He notes that conversations between potential mates cannot be talking just for the sake of talking. There should be a firm and clear intention of either pursuing engagement and marriage, or, if one of the two or both the man and woman feel they are not compatible, a quick end to the relationship.
This ensures both sides are safe from getting hurt more than they could in this kind of a situation and remain within the bounds of Islam, In shaa Allah.
With regards to questions pertaining to a person’s sexual history (for example, has s/he had a boy/girlfriend, does s/he have any type of sexually transmitted diseases), Imam Nur Abdullah says these things have to be investigated at the very beginning, when the communication for marriage begins. This is not something that should be brought up at the last stage.
Other topics that should also be discussed at the early stages include level of Islamic knowledge and practice, future career and education plans, home making skills and where the couple will live right after marriage and in the future (state and/or country, with in-laws or in their own apartment/home).
The Imam also says the couple can even get a blood test to ensure both are healthy. Some states require this before marriage.
Seeking marriage is something highly recommended in Islam. While looking for a potential mate should be something Muslims help each other with, this cannot be done at the expense of Islamic rules pertaining to modesty and respect between the sexes.
While trying your best, never stop praying to Allah to grant you your wish. Following are the dua’s that you can recite:
1.Perform your obligatory prayer and after every prayer recite this dua you will get a good husband/wife when the time’s come in shaa Allah,
"Our Lord, grant us from among our wives and offspring comfort to our eyes and make us an example for the righteous." (Quran 25:74)
2.Rabbi inni lemaa anzalta elayya min khairin faqeer (Chapter 28, verse 24)
My Lord! I am needy of whatever good You Send down for me
So, what you have to do is after you read this verse a number of times; make sure to ask Allah (God) in a way similar to what follows:
 "Oh Allah! You have made every living thing in pairs. The sincere, beautiful and pious pair that you have created for me, please give it to me"
It is recommended that one recites this verse at least 10times and after finishing this dua ask Allah Almighty for a spouse that is kind, beautiful, soft hearted, pious, loving and a gentle soul mate. What you want in your spouse is what you should ask but if you don’t ask for piety or kind heartedness then don’t blame anyone but yourself.
3.”Rabbana aatina fi’d dunya hasana wa fi’l aakhirati hasana wa qina `adhab an-nar.” [O Lord! Grant us good in this life, and good in the next, and save us from the torment of the Fire] (Qur’an, 2: 200). Recite this dua’ with the intention of marriage as it is included in the phrase “fi’d dunya hasana” (good in this life).
4.My Lord, do not leave me alone and You are the best of inheritors. (Surah al-Anbiya` 21:89)
I hope it will be helpful. May Allah guide us all to the straight path.
Ameen